PRODUCTION OF RECOMBINANT POLYPEPTIDES BY BOVINE SPECIES AND TRANSGENIC METHODS

Abstract: A transgene for producing recombinant polypeptides in the milk of transgenic bovine species comprises at least one expression regulation sequence, a secretory DNA sequence encoding a secretory signal sequence which is functional in mammary secretory cells of the bovine species and a recombinant DNA sequence encoding the recombinant polypeptide. Also included are methods for producing transgenic bovine species. The method includes introducing the above transgene into an embryonal target cell of a bovine species, transplanting the trangenic embryonic target cell formed thereby into a recipient bovine parent and indentifying at least one female offspring which is capable of producing the recombinant polypeptide in its milk. The invention also includes transgenic bovine species as well as the milk from such transgenic bovine species. Methods are also provided for producing transgenic non-human mammals having a desirable phenotype. The method comprises first methylating a transgene followed by introduction into fertilized oocytes. The oocytes are then cultured to form pre-implantation embryons. Thereafter, at least one cell is removed from each of the pre-implantation embryons and the DNA digested with a restriction endonuclease capable of cleaving the methylated transgene but incapable of cleaving the unmethylated form of the transgene.

Description: PRODUCTION OF RECOMBINANT POLYPEPTIDES BY BOVINE SPECIES AND TRANSGENIC METHODS Field of the Invention The invention relates to the production of recombinant polypeptides by transgenic bovine species and to methods for producing transgenic non-human mammals having a desired phenotype. Background of the Invention There is a plethora of literature relating to the expression of heterologous genes in lower organisms such as unicellular bacteria, yeast and filamentous fungi, and in higher cell types such as mammalian cells. There are also numerous reports on the production of transgenic animals, most of which relate to the production of transgenic mice. See, e.g., U.S. Pat. No. 4,736,866 (transgenic mice containing activated oncogene) ; Andres, A., et al. (1987) Proc. Natl. Acad. Sci. USA 8_4-' 1299-1303 (HA-RAS oncogene under control of whey acid protein promoter) ; Schoenberger, CA. , et al. (1987) Experientia 43:644 and (1988) EMBO J. 7: 169-175 (C-myc oncogene under control of whey acid protein promoter) ; and Muller, W.J., et al. (1988) Cell 54 : 105- 115 (C-myc oncogene under control of the mouse mammary tumor virus promoter) . Several laboratories have also reported the production of transgenic porcine species (Miller, K.F., et al. (1989) J. Endocrin. 120:481-488 (expression of human or bovine growth hormone gene in transgenic swine) ; Vize, P.D., et al. (1988) J. Cell Sci. 9 . 0-295-300 (porcine growth hormone fusion gene in transgenic pigs) ; and Ebert, K. et al. (1988) Mol. Endocrin. 2 : 277-283 (MMLV-rat so atotropin fusion gene in transgenic pigs) ) , transgenic sheep (Nancarrow, et al. (1987) Theriogenology 2J7:263 (transgenic sheep containing bovine growth hormone gene) Clark, A.J. et al. (1989) Bio/Technology 7:487-482 and Simons, J., et al. (1988) Bio/Technology 6: 179-183 (human factor IX and α-1 antitrypsin CONA in ovine species) , and rabbit (Hanover, S.V., et al. (1987) Deutche Tierarztliche Wochenschrift 9 _, : 476-478 (production of transgenic ' rabbits by injection of uteroglobin-promoter-CAT fusion gene into fertilized rabbit oocytes) . A number of reports have also suggested the production of transgenic cattle (Wagner, et al. (1984) Theriogenology 21:29-44) with one reporting some progress in microinjection techniques (Lohse, J.K., et al. (1985) Theriogenology 2_3:205) . However, little, if any, success has been achieved in producing transgenic cows. Scientific articles which clearly demonstrate the actual production of a transgenic cow capable of producing a heterologous protein are presently unknown. This, despite the statements that one transgenic cow was produced in Canada which expressed human β-interferon (Van Brunt, J. (1988) Bio/Technology 6:1149-1155) and that transient expression of human α-fetoprotein in liver and blood was obtained on one occasion (Church, R.B. (1986) Biotechnology News Watch 6 . (15) , 4) . One reference reports that bovine papilloma virus was apparently integrated but not expressed in a transgenic cow (Roschlau, et al. (1988) Arch. Tierz . , Berlin 31 : 3-8) . A recent article has summarized the genetic engineering of livestock. (Pursel, V.G. et al. (1989) Science 244: 1281-1288) . A number of laboratories have reported tissue-specific expression of DNA encoding various proteins in the mammary gland or the production of various proteins in the milk of transgenic mice and sheep. For example, Simmons, J.P., et al. (1987) Nature 328:530-532 report the microinjection of a 16.2 kb genomic fragment encoding β-lactcglobulin (BLG) including 4 kb of 5' sequence, 4.9 kb of the BLG transcription unit and 7.3 kb of 3' flanking sequence into fertilized mouse eggs. According to these authors, the sheep BLG was expressed in mammary tissue and produced BLG in the milk of the transgenic mice at concentrations ranging from about 3.0 to about 23 mg/ml. When, however, cDNA encoding human factor IX or human αl-antitrypsin was inserted into the 5 ' untranslated region of the BLG gene and microinjected into sheep (Simmons, J.P., et al. (1988) Bio/Technoloσy 6 : 179-183) the production of factor IX or αl-antitrypsin was significantly reduced (25ng/ml for factor IX and lOmg/ml for αl-antitrypsin; see Clark, A.J., et al. (1989) Bio/Technology 2=487- 492) . In a similar approach, a 14 kb genomic clone containing the entire 7.5 kb rat 0-casein together with 3.5 kb of 5' and 3.0 kb of 3' flanking DNA was reportedly microinjected into fertilized mouse oocytes. Lee, et al. (1988) Nucl. Acids Res. 16:1027-1041. Yet, in this case, the level of expression of the rat 3-transgene in the lactating mammary gland of transgenic mice was reported to be at a level of 0.01-1% of the endogenous mouse -casein gene. Human tissue plasminogen activator (t-PA) reportedly was produced in transgenic mouse milk at the levels between 0.2 and about 0.4μg/ml when a cDNA encoding a human t-PA with its endogenous secretion sequence was expressed under control of a 2.6 kb 5 ' sequence of the murine whey acid protein gene. Gordon, K., et al. (1987) Bio/Technology 5_: 1183-1187. Subsequent experiments using the same or similar construction reportedly produced t-PA in different mouse lines arranging from less than 20ng of t-PA per ml of milk to about 50μg/ml. Pittius, C.W. , et al. (1988) Proc. Natl. Acad. Sci. USA 85:5874-5878. U.S. Patent No. 4,873,316 issued October 10, 1989, discloses the use of 9 kb of 5 ' sequence from the bovine αSl casein gene including the casein signal peptide and several casein codons fused to a mature t-PA sequence. The transgenic mice obtained with this construct reportedly produced about 0.2-0.5μg/ml of a t-PA fusion protein in their milk. In addition, a number of patent publications purportedly describe the production of specific proteins in the milk of transgenic mice and sheep. See, e.g. European Patent Publication No. 0 264 166 published April 20, 1988 (hepatitis B surface antigen and t-PA genes under control of the whey acid promoter protein for mammary tissue specific expression in mice) ; PCT Publication No. W088/00239 published January 14, 1988 (tissue specific expression of a transgene encoding factor IX under control of a whey protein promoter in sheep) ; PCT Publication No. W088/01648 published March 10, 1988 (transgenic mouse having mammary secretory cells incorporating a recombinant expression system comprising a bovine α-lactalbumin gene fused to interleukin-2) ; European Pat. Pub. No. 0 279 582 published August 24, 1988 (tissue-specific expression of chloramphenicol acetyltransferase under control of rat /3-casein promoter in transgenic mice) ; and PCT Pub. No. W088/10118 published December 29, 1988 (transgenic mice and sheep containing transgene encoding bovine αSl casein promoter and signal sequence fused to t-PA) . Given the state of the transgenic art, it is apparent that a need exists for methods which enable the efficient production of transgenic mammals, especially transgenic mammals other than transgenic mice. Further, it is apparent that a need exists for methods for producing transgenic bovine species which are capable of producing recombinant polypeptides such as human milk proteins and human serum proteins in the milk of such transgenic mammals. Accordingly, it is an object herein to provide methods for detecting the transgenesis of fertilized oocytes prior to implantation. In addition, it is an object herein to provide transgenic bovine species which are capable of producing recombinant polypeptides which are maintained intracellularly or are secreted extracellularly. It is also an object herein to provide transgenic bovine species which are capable of producing recombinant polypeptides such as human milk proteins and human serum proteins in the milk of such transgenic animals. Further, it is an object herein to provide milk from a transgenic bovine species containing such recombinant polypeptides. Still further, it is an object herein to provide food formulations supplemented with recombinant polypeptides from such transgenic milk such as human infant formula supplemented with human lactoferrin. Further, it is an object herein to provide transgenes which are capable of directing the production of recombinant polypeptides in the milk of transgenic bovine species. The references discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate such disclosure by priority based on earlier filed applications. Summary of the Invention In accordance with the above objects, the invention includes transgenes for producing recombinant polypeptides in the milk of transgenic bovine species. The production of such transgenic bovine milk containing one or more recombinant polypeptides is desirable since it provides a matrix wherein little or no purification is necessary for human consumption. The transgene comprises a secretory DNA sequence encoding a secretory signal sequence which is functional in mammary secretory cells of the bovine species of interest and a recombinant DNA sequence encoding the recombinant polypeptide. These sequences are operably linked to form a secretory-recombinant DNA sequence. At least one expression regulation sequence, functional in the mammary secretory cells of the bovine species, is operably linked to the secretory-recombinant DNA sequence. The transgene so constructed is capable of directing the expression of the secretory-recombinant DNA sequence in mammary secretory cells of bovine εpecies containing the transgene. Such expression produces a form of recombinant polypeptide which is secreted from the mammary secretory cells into the milk of the transgenic bovine species. In addition, the invention includes methods for producing such transgenic bovine species. The method includes introducing the above transgene into an embryonal target cell of a bovine species, transplanting the transgenic embryonic target cell formed thereby into a recipient bovine parent and identifying at least one female offspring which is capable of producing the recombinant polypeptide in its milk. The invention also includes transgenic bovine species capable of producing recombinant polypeptides in the milk of lactating females of said species, the milk from such transgenic bovine species containing such recombinant polypeptides and food formulations containing the transgenic milk in liquid or dried form, as well as food formulations supplemented with one or more recombinant polypeptides from such transgenic milk. In addition to the foregoing, the invention includes transgenes and transgenic bovine species containing transgenes that are capable of producing a recombinant polypeptide. Such transgenes are similar to the aforementioned transgenes for milk secretion and are characterized by having an expression regulation sequence which targets the expression of the DNA encoding the recombinant polypeptide to a particular cell or tissue type, e.g. expression of human serum albumin in the liver of a transgenic bovine species. When the recombinant polypeptide is to be secreted from such targeted cells or tissues, a secretory DNA sequence encoding a secretory signal sequence functional in the particular targeted cell or tissue is operably linked to the recombinant DNA sequence encoding the recombinant polypeptide, e.g. secretion of human serum albumin from bovine liver into the bovine circulatory system. Further, the invention includes methods for producing transgenic non-human mammals having a desirable phenotype. The method comprises first causing the methylation of a transgene capable of conferring the desirable phenotype when incorporated into the cells of a transgenic non-human animal, e.g., by transforming an appropriate bacterium, such as E. coli MM 294, with a plasmid containing the transgene. The methylated transgene is then excised and introduced into fertilized oocytes of the non-human animal to permit integration into the genome. The oocytes are then cultured to form pre-implantation embryos thereby replicating the genome of each of the fertilized oocytes. Thereafter, at least one cell is removed from each of the pre-implantation embryos and treated to release the DNA contained therein. Each of the released DNAs are then digested with a restriction endonuclease capable of cleaving the methylated transgene but incapable of cleaving the unmethylated form of the transgene formed after integration into and replication of the genomic DNA. Those pre-implantation embryos which have integrated the transgene contain DNA which is resistant to cleavage by the restriction endonuclease in the region containing the transgene. This resistance to digestion, which can be detected by electrophoresis of the digest after PCR amplification of the DNA and hybridization with a labelled probe for the transgene, facilitates the identification of successful transgenesis. The invention also includes a method to produce a population of transgenic offspring having the same genotype. This method utilizes a specific embodiment of the above method for detecting early transgenesis. In this method, a methylated transgene is introduced into fertilized oocytes which are cultured to pre- implantation embryos. Thereafter, each pre-implantation embryo is divided to form first and second hemi-embryos. Each of the first hemi-embryos are then analyzed for transgenesis as described above. After identifying successful transgenesis in at least one first hemi-embryo, the second untreated hemi-embryo which contains the integrated transgene, is cloned to form a multiplicity of clonal transgenic blastocysts or hemi- blastocysts, each of which have the same genotype. The transgenic embryos are thereafter transplanted into one or more recipient female parents to produce a population of transgenic non-human mammals having the same genotype. Brief Description of the Drawings The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: Fig. 1 depicts the DNA (Seq. ID No.: 1) and amino acid (Seq. ID No. : 2) sequence for a human lactoferrin clone derived from a human mammary cDNA library as described herein except that the sequence between nucleotides 1557-1791 and 2050-2119 corresponds to the previously published sequence (Rado et al. (1987) Blood 70: 989- 993) . Fig. 2 depicts the complete DNA (Seq. ID No.: 3) and amino acid (Seq. ID No. : 4) sequence of human lactoferrin including 5' and 3 1 untranslated sequence as well as the complete human lactoferrin signal sequence. Fig. 3 is a restriction nap or a clone of a 5' -flanking region of bovine αSl casein gene. Fig. 4 is a restriction map ol a clone of a 3' -flanking region of bovine αSl casein gene. Figs. 5A, 5B and 5C depict the construction of pSI3'5'CAT and pSI5'CAT. Fig. 6 depicts pMH-1. Figs. 7A through 7F depict the construction of expression vectors containing sequences encoding human lactoferrin. Fig. 8 depicts the genome or human serum albumin, the fragments used to generate transgenic mice contained in this genomic DNA and the identification of the fragment sizes which ..ould be obtained upon the digestion of genomic DNA from a transgenic mouse with the restriction enzymes BstE-II and Nco-I or '-ith Nco-I and Hindi-Ill. Fig. 9 depicts an alternate path'..ay for the construction of a transgene of the invention encoding human lactoferrin. Fig. 10 depicts the construction of a plasmid pPC containing a transgene encoding Protein C. Fig. 11 depicts the DNA sequence for a hybrid intervening sequence used in a preferred embodiment of the invention. This hybrid sequence comprises a 5' portion from an intervening sequence of bovine αSl casein and a 3 ' portion from an intervening sequence of an IgG intervening sequence. The juncture of the 5' and 3' portion is the Hindlll site shown. Fig. 12A is a restriction map of a bovine αSl casein promoter hLF cDNA transgene. Fig. 12B shows a Southern blot analysis of DNA isolated from various bovine and murine tissues using an hLF cDNA probe. Fig. 13 depicts restriction maps of hLF genomic clones 13.1 and 13.2. Fig. 14 depicts the BamHI fragment from genomic hLF subcloned into plasmid pUC19. Fig. 15A depicts a restriction map of the 8hLFgen9k or 16hLFgen9k construct containing the 8 or 16 kb αSl casein promoter, a Clal-Apal synthetic linker and the 9 kb (i.e. , 8.9 kb) Apal-Sall genomic hLF fragment. Fig. 15B depicts the DNA sequence of the Clal-Apal synthetic sequence shown in Fig. 15A. Fig. 15C depicts the IVS and the structure of exon 1 and part of exon 2 of the genomic hLF construct shown in Fig. 15A through Fig. 17. Fig. 16 depicts the coinjection of the Notl-Sall fragment from the 8hLFgen9k or 16hLFgen9k construct (as shown in Fig. 15A) with the 3 1 Clal fragment of genomic hLF. Fig. 17 depicts the generation of a genomic 8hLF transgene by linking the Notl-Mlul fragment from the 8hLFgen9k construction (shown in Fig. 15A) , the Mlul- Clal fragment from clone 13.2 depicted in Fig. 13 and a Clal-NotI linker. Fig. 17 also depicts the DNA sequence of the Clal-NotI linker. Figs. 18-20 depict the generation of the 0LG-hLFgen and LG-hLFgen37 constructs. Fig. 21 depicts the design of the 16,8hLZ expression vector. Fig. 22 depicts the design of the 16,8hLZ3 expression vector. Fig. 23A-23E depict the pathway for the construction of plasmid pl6,8hLZ. Fig. 24 depicts a comparison between the DNA of bovine μLG and sheep JLG. The top sequence represents the bovine sequence. Fig. 25 shows the linker GP 278/279. Fig. 26 depicts the pl6,8A hLZ3 expression vector. Fig. 27 depicts the 16,A hLZ3 expression vector. Detailed Description of the Invention The "non-human mammals" of the invention comprise all non-human mammals capable of producing a "transgenic non-human mammal" having a "desirable phenotype". Such mammals include non-human primates, murine species, bovine species, canine species, etc. Preferred non- human animals include bovine, porcine and ovine species, most preferably bovine species. Desirable phenotypes for transgenic non-human mammals include, but are not limited to, the production of recombinant polypeptides in the milk of female transgenic non-human mammals, the production of animal models for the study of disease, the production of animals with higher resistance to disease (e.g. diseases of the mammary gland such as mastitis) and the production of recombinant polypeptides in the blood, urine or other suitable body fluid or tissue of the animal. In the preferred embodiments, transgenic bovine species are disclosed which are capable of producing recombinant human lactoferrin, human serum albumin and human Protein C in the milk of lactating females or human serum albumin in the liver of the transgenic animal. The transgenic non-human mammals of the invention are produced by introducing a "transgene" into an embryonal target cell of the animal of choice. In one aspect of the invention, a transgene is a DNA sequence which is capable of producing a desirable phenotype when contained in the genome of cells of a transgenic non- human mammal. In specific embodiments, the transgene comprises a "recombinant DNA sequence" encoding a "recombinant polypeptide". In such cases, the transgene is capable of being expressed to produce the recombinant polypeptide. As used herein, a "recombinant polypeptide" (or the recombinant DNA sequence encoding the same) is either a "heterologous polypeptide" or a "homologous polypeptide". Heterologous polypeptides are polypeptides which are not normally produced by the transgenic animal. Examples of heterologous polypeptides include human milk proteins such as lactoferrin, lysozyme, secreted immunoglobulins, lactalbumin, bile salt-stimulated lipase, etc., human serum proteins such as albumin, immunoglobulins, Factor VIII, Factor IX, protein C, etc. and industrial enzymes such as proteases, lipases, chitinases, and liginases from procaryotic and eucaryotic sources. The recombinant DNA sequences include genomic and cDNA sequences encoding the recombinant polypeptide. When recombinant DNA sequences encoding a heterologous polypeptide are used, the transgene may be integrated in a- random manner into the genome of the species used for transgenesis. As disclosed in the Examples, transgenes encoding human lactoferrin, human serum albumin and human Protein C in conjunction with a αSl casein secretory signal sequence under control of αSl casein expression regulation sequences are designed to produce and secrete these heterologous polypeptides from the mammary gland of a lactating transgenic mammal into its milk. As used herein, a homologous polypeptide is one which is endogenous to the particular transgenic species. Examples of endogenous polypeptides from bovine species include bovine- milk proteins such as αSl, αS2 , β- and «-casein, 0-lactoglobulin lactoferrin, lysozyme, cholesterol hydrolase, serum proteins such as serum albumin and proteinaceous hormones such as growth hormones. When recombinant DNA sequences encoding a homologous polypeptide are used, the transgene is preferably integrated in a random manner into the genome of the species used for transgenesis. Such random integration results in a transgenic animal which contains not only the transgene encoding the endogenous polypeptide but also the corresponding endogenous genomic DNA sequence. Accordingly, such transgenic non- human mammals are readily characterized by an increase in the copy number of genes encoding the endogenous polypeptide. Further, the transgene will generally be located at a position which is different from the endogenous gene. When DNA encoding a homologous polypeptide is expressed, for example, in bovine species, the transgenic animal is characterized by an increase in the amount of the homologous polypeptide in either the endogenous tissue or fluid in which it is normally found and/or by its presence in a tissue and/or body fluid which either does not normally contain the homologous polypeptide or produces it at significantly lower levels. Thus, for example, bovine cholesterol hydrolase is normally present in the colostrum for about the first 15-20 days of lactation. This naturally occurring endogenous polypeptide increases calf weight. This protein, however, is also a homologous polypeptide when, for example, its expression in mammary secretory cells is placed under the control of expression regulation sequences, such as those obtained from bovine casein genes, which facilitate the expression of the homologous polypeptide beyond the lactation period that it is normally present. Thus, according to one aspect of the invention, bovine cholesterol hydrolase expression is maintained in transgenic bovine milk by placing the expression of cholesterol hydrolase recombinant DNA (either cDNA or genomic) under the control of bovine αSl casein expression regulation sequences. When a genomic recombinant DNA is used, it is engineered such that it has appropriate restriction sites (e.g. Clal and Sail) at the 5' and 3 1 end of the structural gene such that it is capable of being inserted into an appropriate transgene genomic cassette (e.g. p-16 kb, CS which is described in Example 15) . Alternatively, a recombinant DNA encoding bovine cholesterol hydrolase derived from cDNA may be placed under control of bovine αSl casein expression regulation sequence by substituting the human lactoferrin sequences in a plasmid such as pl6, 8HLF3 (containing a hybrid intervening sequence) or pl6, 8HLF4 (containing a homologous αSl casein intervening sequence) . When these particular plasmids are used, the cDNA clone is engineered such that it has appropriate Clal and Sail restriction sites at the ends of the recombinant DNA. By way of further example, bovine lactoferrin is normally present in only trace amounts in cow's milk. When, however, bovine lactoferrin is expressed under control of other regulatory sequences, for example, obtained from an αSl casein gene, higher amounts of lactoferrin in the milk of transgenic bovine species are obtained. In another example, a transgene comprising DNA encoding homologous bovine growth hormone is incorporated into the bovine genome to confer superior growth characteristics to the transgenic animal. In other instances, homologous polypeptides include, for example, a polypeptide v.'hich normally is maintained intracellularly in a particular species but which is secreted into the milk or other extracellular compartment of the transgenic species, such as the circulatory system. Each of the heterologous or homologous polypeptides are characterized by specific amino acid and nucleic acid sequences. It is to be understood, however, that such sequences include naturally occurring allelic variations thereof and variants produced by recombinant methods wherein such nucleic acid and polypeptide sequences have been modified by the substitution, insertion and/or deletion of one or more nucleotides in such nucleic acids to cause the substitution, insertion or deletion of one ore more amino acid residues in the recombinant polypeptide. When expression of the DNA of the transgene is necessary to generate a desired phenotype, e.g. to produce a recombinant polypeptide, the transgene typically includes at least a 5 ' and preferably additional 3 ' "expression regulation sequences" each operably linked to a recombinant or secretory-recombinant DNA as defined hereinafter. Such expression regulation sequences in addition to controlling transcription also contribute to RNA stability and processing, at least to the extent they are also transcribed. Such expression regulation sequences are chosen to produce tissue-specific or cell type-specific expression of the recombinant or secretory-recombinant DNA. Once a tissue or cell type is chosen for expression, 5' and optional 3' expression regulation sequences are chosen. Generally, such expression regulation sequences are derived from genes that are expressed primarily in the tissue or cell type chosen. Preferably, the genes from which these expression regulation sequences are obtained are expressed substantially only in the tissue or cell type chosen, although secondary expression in other tissue and/or cell types is acceptable if expression of the recombinant DNA in the transgene in such tissue or cell type is not detrimental to the transgenic animal. Particularly preferred expression regulation sequences are those endogenous to the species of animal to be manipulated. However, expression regulation sequences from other species such as those from human genes may also be used. Particularly preferred expression regulation sequences from human genes are human lactoferrin (hLF) sequences. In some instances, the expression regulation sequences and the recombinant DNA sequences (either genomic or CDNA) are from the same species, e.g., each from bovine species or from a human source. In such cases, the expression regulation sequence and the recombinant DNA sequence are homologous to each other. Alteratively, the expression regulation sequences and recombinant DNA sequences (either cDNA or genomic) are obtained from different species, e.g., an expression regulation sequence from bovine species and a recombinant DNA sequence from a human source) . In such cases, the expression regulation and recombinant DNA sequence are heterologous to each other. The following defines expression regulation sequences from endogenous genes. Such definitions are also applicable to expression regulation sequences from non-endogenous, heterologous geneε. In general, the 5' expression regulation sequence includes the transcribed portion of the endogenous gene upstream from the translation initiation sequence (the 5' untranslated region or 5' UTR) and those flanking sequences upstream therefrom which comprise a functional promoter. As used herein, a "functional promoter" includes those necessary untranscribed DNA sequences v/hich direct the binding of RNA polymerase to the endogenous gene to promote transcription. Such sequences typically comprise a TATA sequence or box located generally about 25 to 30 nucleotides from the transcription initiation site. The TATA box is also sometimes referred to the proximal signal. In many instances, the promoter further comprises one or more distal signals located upstream from the proximal signal (TATA box) which are necessary to initiate transcription. Such promoter sequences are generally contained within the first 100 to 200 nucleotides located upstream from the transcription initiation site, but may extend up to 500 to 600 nucleotides from the transcription initiation site. Such sequences are either readily apparent to those skilled in the art or readily identifiable by standard methods. Such promoter sequences alone or in combination with the 5' untranslated region are referred to herein as "proximal 5' expression regulation sequences". In addition to such proximal 5' expression regulation sequences, it is preferred that additional 5' flanking sequences (referred to herein as "distal 5' expression regulation sequences") also be included in the transgene. Such distal 5' expression regulation sequences are believed to contain one or more enhancer and/or other sequences which facilitate expression of the endogenous gene and as a consequence facilitate the expression of the recombinant or secretory-recombinant DNA sequence operably linked to the distal and proximal 5' expression regulation sequences. The amount of distal 5' expression regulation sequence depends upon the endogenous gene from which the expression regulation sequences are derived. In general, however, such sequences comprise 5' flanking regions of approximately 1 kb, more preferably 16 kb and most preferably about 30 kb of 5' flanking sequence. The determination of the optimal amount of distal 5' expression regulation sequence used from any particular endogenous gene is readily determined by varying the amount of distal 5" expression regulation sequence to obtain maximal expression. In general, the distal 5' expression regulation sequence will not be so large as to extend into an adjacent gene and will not include DNA sequences which adversely effect the level of transgene expression. In addition, it is preferred that 3' expression regulation sequences also be included to supplement tissue or cell-type specific expression. Such 3' expression regulation sequences include 3 ' proximal and 3 ' distal expression regulation sequences from an appropriate endogenous gene. The 3' proximal expression regulation sequences include transcribed but untranslated DNA positioned downstream from the translation stop signal in the recombinant DNA sequence (also referred to as the 3' untranslated region or 3' UTR) . Such sequences generally terminate at a polyadenylation sequence (either from the endogenous gene or from other sources such as SV40) and sequences that may affect RNA stability. Generally, 3' UTR's comprise about 100 to 500 nucleotides downstream from the translation stop signal in the gene from which the 3' regulation sequence is derived. Distal 3' expression regulation sequences include flanking DNA sequences downstream from the proximal 3 ' expression regulation sequence. Some of these distal sequences are transcribed, but do not form part of the mRNA while other sequences in this distal ' expression regulation sequence are not transcribed at all. Such distal 3' expression regulation sequences are believed to contain enhancer and/or other -sequences which enhance expression. Such sequences are believed to be necessary for efficient polydenylation and contain transcription termination sequences Preferably, such sequences comprise about 2 kb, more preferably 8 kb and most preferably about 15 kb of 3' flanking sequence. A preferred 3 ' flanking sequence is the 3 ' flanking sequence of the human lactoferrin (hLF) gene. Transgenic animals containing transgenes that include about 9 kb of hLF 3 ' flanking sequences show enhanced expression of recombinant polypeptides in milk compared to animals containing transgenes that include 1 kb or less of hLF 3" flanking sequence, due to an enhancer or other enhancing sequence located in this region. Usually the human lactoferrin 3' flanking sequence will be at least 1 kb in length up to about 9 kb in length or longer, typically 3 to 7 kb, more typically 4 to 5 kb. It will also be possible, and sometimes desirable, to use standard methods (e.g., deletion analysis) to identify regions contained within the 9 kb 3 ' flanking sequence that enhance mammary gland expression of recombinant polypeptides. These enhancers or enhancing sequences can be isolated and used in combination with various amounts of homologous or heterologous sequences. Typically the enhancing sequences can range in length from about 50 basepairs to about 2 kb, more typically from about 100 basepairs to about 500 basepairs. It will often be desirable to use a transgene having a 5 ' expression regulation sequence and a 3 ' flanking sequence that originate from the same gene. In a preferred embodiment, the 5' expression regulation sequence and 3 ' flanking sequence are from the bovine αSl-casein gene. In an alternative embodiment a genomic sequence, such as a human genomic clone or clones, can be introduced into an animal to produce a transgenic animal containing a transgene that has the sequence of the human gene, including all or part of the 5' expression regulation sequences, coding sequences, introns, and 3' untranslated and flanking sequences. In a preferred embodiment, the human lactoferrin genomic sequence is used in its entirety, but various components can be substituted with components from other mammary gland specific genes. Although the use of both 5' and 3' expression regulation sequences are preferred, in some embodiments of the invention, endogenous 3' regulation sequences are not used. In such cases,, the 3' proximal expression regulation sequences normally associated with the genomic DNA encoded by the recombinant DNA sequence are used to direct polyadenylation. In addition, distal 3' regulation sequences from the genomic DNA encoding the recombinant polypeptide may also be employed preferably in the same amounts as set forth for endogenous 3 ' expression regulation sequences. In such cases, it is to be understood that the recombinant polypeptide encoded by the transgene may comprise either genomic DNA or a double stranded DNA derived from cDNA. As with the 5' expression regulation sequences, the optimal amount of 3 ' expression regulation sequence may be readily determined by varying the amount of 3 ' flanking sequence to obtain maximal expression of the recombinant polypeptide. In general, the distal 3 1 regulation sequence, be it from an endogenous gene or a heterologous gene, will not extend into the adjacent gene from which is derived and will exclude any sequences which adversely effect the level of transgene expression. Examples of expression regulation sequences are provided in Table I. TABLE 1 Expression Regulation Tissue Animal Sequence Specificity Species 16 kb of bovine αSl Mammary bovine casein 5' to structural secretory gene and 8 kb 3 ' to cells structural gene -15 kb 5 ' to albumin Liver murine gene ~15 kb 5' to α-actin Muscle murine gene ~15 kb upstream of Spermatids murine prota ine gene In addition to the 5' and 3' expression regulation sequences and the recombinant DNA (either genomic or derived from cDNA) the transgenes of the invention preferably also comprise a "recombinant intervening sequence" which interrupts the transcribed but untranslated 5' region of the transgene. Such intervening sequences can be derived, for example, from bovine αSl casein and from human lactoferrin. Such sequences as used herein are "homologous recombinant intervening sequences" in that the 5' and 3' RNA splice signals in such recombinant intervening sequences are those normally found in an intervening sequence from an endogenous or heterologous gene. Recombinant intervening sequences may, however, also comprise a "hybrid intervening sequence". Such hybrid intervening sequences comprise a 5' RNA splice signal and 3' RNA splice signal from intervening sequences from different sources. In some aspects of the invention, such hybrid intervening sequences comprise at least one "permissive RNA splice sequence". As used herein, a permissive RNA splice signal is an RNA splice signal sequence, preferably a 3' RNA splice signal, from an intron contained within a repertoire of germ line DNA segments which undergo rearrangement during cell differentiation. Examples of such gene repertoires include the immunoglobulin super gene family, including the immunoglobulins and T-cell antigen receptors as well as the repertoire of the major histocompatibility complex (MHC) genes and others. Particularly preferred permissive splice sequences are those obtained from the immunoglobulin repertoire, preferably of the IgG class, and more preferably those 3 ' splice signal sequences associated with the J-C segment rearrangement of the Ig heavy and light chain, most preferably the heavy chain. A particularly preferred permissive splice sequence comprises that portion of the sequence as shown downstream of the Hindlll site in Fig. 11. A particularly preferred hybrid intervening sequence comprises the entire sequence shown in Fig. 11 which includes a 5 ' portion of an intervening sequence from bovine αSl casein and a 3 ' sequence portion of an IgG heavy chain intervening sequence. Such hybrid intervening sequences containing permissive RNA splice signals are preferably used when the recombinant DNA corresponds to a cDNA sequence. As indicated in the Examples, when 16 kb of 5' expression regulation sequence from the αSl casein gene was used in conjunction with an αSl casein-IgG hybrid intervening sequence to express human lactoferrin cDNA operably linked to the αSl casein secretory signal sequence a transgenic mouse was obtained which produced approximately 1330 μg/ l of hLF in the transgenic milk. This amount of recombinant polypeptide far exceeds the previously reported amounts for production of various protein in transgenic mouse milk of generally less than 10 μg/ml and in one case approximately 50 μg/ml. It also exceeds the maximum of 8μg/ml of hLF produced herein when the same transgene was used that contained a homologous bovine intervening sequence rather than the hybrid intervening sequence. However, such hybrid intervening sequences are not limited to transgenes utilizing cDNA sequence. Rather, hybrid intervening sequences are also useful when the recombinant polypeptide is encoded by a genomic sequence. Based on the results obtained with the cDNA recombinant DNA and the general expectation that genomic DNA sequences express at higher levels than sequences derived from cDNA, it is expected that such hybrid intervening sequences used in conjunction with genomic recombinant DNA will further enhance expression levels above that which would otherwise be obtained with genomic sequence alone. Based on the foregoing, it is apparent that preferred transgenes include large amounts of 5' and 3' expression regulation sequences. Further, the recombinant DNA is preferably derived from genomic clones which may be tens to hundreds of kilobases in length. Based on the present technology for cloning and manipulating DNA, the construction and microinjection of transgenes is practically limited to linearized DNA having a length not greater than about 50 kb. However, the transgenes of the invention, especially those having a length greater than about 50 kb, may be readily generated by introducing two or more overlapping fragments of the desired transgene into an embryonal target cell. When so introduced, the overlapping fragments undergo homologous recombination which results in integration of the fully reconstituted transgene in the genome of the target cell. In general, it is preferred that such overlapping transgene fragments have 100% homology in those regions which overlap. However, lower sequence homology may be tolerated provided efficient homologous recombination occurs. If non-homology does exist between the homologous sequence portions, it is preferred that the non-homology not be spread throughout the homologous sequence portion but rather be located in discrete areas. Although as few as 14 base pairs at 100% homology are sufficient for homologous recombination in mammalian cells (Rubnitz, J. and Subramani, S. (1984) Mol. Cell. Biol. 4_: 2253-2258) , longer homologous sequence portions are preferred, e.g. 500bp, more preferably lOOObp, next most preferably 2000bp and most preferably greater than 2000bp for each homologous sequence portion. As indicated in the . examples, three overlapping fragments of the human serum albumin gene were microinjected into the pronuclei of mouse zygotes in approximately equal molar portions. These fragments successfully recombined and integrated into the mouse genome as confirmed by analysis of the integrated DNA by Southern blotting procedures and by detection of RNA transcript and human serum albumin in the serum of the transgenic mouse. Although the transgene so generated has a unit length of 38 kb, there is no known practical limit to the size of the transgene which may be formed using larger and/or greater numbers of overlapping transgene fragments. In particular, it is expected that transgenes may be formed by this approach having lengths between about 50 to 1000 kb and more preferably between 50 and 500 kb. Further, the use of homologous recombination of overlapping fragments is expected to be fruitful in the generation of larger transgenic animals, such as transgenic bovine species, containing transgenes incorporating recombinant DNA comprising genomic DNA which otherwise could not be incorporated into a pronucleus to form a transgenic animal. Such genomic transgenes are expected to produce higher expression levels in transgenic cows as compared to that which is produced by transgenes encoding recombinant cDNA. When, the ultimate object is to secrete a recombinant polypeptide, a "secretory DNA sequence" encoding a functional secretion signal peptide is also operably linked within the transgene to direct secretion of the recombinant polypeptide from one or more cell types within the transgenic animal. Secretory DNA sequences in general are derived from genes encoding secreted proteins of the same species of the transgenic animal. Such secretory DNA sequences are preferably derived from genes encoding polypeptides secreted from the cell type targeted for tissue-specific expression, e.g. secreted milk proteins for expression in and secretion from mammary secretory cells. Secretory DNA sequences, however, are not limited to such sequences. Secretory DNA sequences from proteins secreted from other cell types within the species of transgenic animal may also be used, e.g., the native signal sequence of a homologous gene encoding a protein secreted other than in the mammary glands. In addition, "heterologous secretory DNA sequences" v/hich encode signal secretion peptides from species other than the transgenic animals my also be used e.g., human t-PA, human serum albumin human lactoferrin and human lactalbumin and secretion signals from microbial genes encoding secreted polypeptides such as from yeast, filamentous fungi, and bacteria. In general, a secretory DNA sequence may be defined functionally as any DNA sequence v/hich when operably linked to a recombinant DNA sequence encodes a signal peptide which is capable of causing the secretion of the recombinant polypeptide. In one of the preferred embodiments, a secretory DNA sequence encoding a secretory signal sequence functional in the mammary secretory cells of bovine species is used to cause secretion of recombinant polypeptide from bovine mammary secretory cells. The secretory DNA sequence is operably linked to the recombinant DNA sequence. Examples of such secretory DNA sequences include DNA sequences encoding signal secretion sequences for bovine αSl casein, murine lactoferrin and human transferrin. The preferred secretory DNA sequence is that encoding the secretory sequence of αSl casein from bovine species. The use of this secretory DNA sequence is described in more detail in the Examples. "Operably linked" in the context of linking a secretory DNA sequence to a recombinant DNA sequence means that the secretory DNA sequence (comprising codons encoding the secretory signal peptide sequence) is covalently coupled to the recombinant DNA sequence so that the resultant secretory-recombinant DNA sequence encodes 5' to 3 ' for the secretory signal sequence and recombinant polypeptide. Accordingly, the reading frame for the secretory sequence and the recombinant DNA sequence must be covalently combined such that an open reading frame exists from the 5' end of the mRNA sequence formed after transcription and processing of the primary RNA transcript. This open reading frame in the RNA contains a 5 ' sequence portion encoding the secretory signal peptide and a 3 ' sequence portion encoding the recombinant polypeptide. When so constructed, the recombinant polypeptide produced upon expression of the secretory-recombinant DNA sequence is of a form which is capable of being secreted from targeted cells which express the DNA sequence. The signal peptide generally is removed in vivo during secretion to produce an extracellular form of the recombinant polypeptide. In the preferred embodiments of the invention, a secretory-recombinant DNA sequence is expressed predominantly in the mammary secretory cells of transgenic bovine species. Such tissue-specific expression is obtained by operably linking mammary specific expression regulation DNA sequences to the above secretory-recombinant DNA sequence. Such mammary specific regulation sequences include the aforementioned regulation sequences contained in various bovine genes preferentially expressed in the mammary secretory cells of the species. Such mammary specific genes include αSl casein; αS2-casein; / 3-casein; K-casein; α-lactalbumin; and -lactoglobulin. Preferred expression regulation sequences are derived from αSl casein as described more in detail in the Examples. In general, the transgenes of the invention that are designed to secrete the recombinant polypeptide into transgenic bovine milk are capable of causing such secretion at levels significantly higher than that previously reported for transgenic mice and sheep. When the recombinant polypeptide is encoded by a recombinant DNA corresponding to, or derived from, cDNA, the molar concentration of the recombinant polypeptide is preferably greater than about 1.0 μM, more preferably greater than about 100 μM, and most preferably greater than 100 μM. When viewed from the perspective of the level of recombinant polypeptide present in the transgenic milk, the amount of recombinant polypeptide is preferably greater than 50 μg/ml, more preferably greater than about 500 μg/ml and most preferably greater than about 1000 μg/ml (lmg/ml) . When the transgene of the invention encodes a recombinant polypeptide that is encoded by recombinant DNA derived from or corresponding to genomic DNA (or comprised substantially of such genomic sequences, e.g. greater than about 50%, more preferably greater than about 75%, most preferably greater than 90% of the codons encoding the recombinant polypeptide are from genomic sequences) , the molar concentrations and protein levels in bovine transgenic milk are the same as for cDNA or higher. In general, the molar concentration of the recombinant polypeptide in such transgenic milk is preferably greater than about 50 μM, more preferably greater than about 150 μM, most preferably greater than about 500 μM. When viev/ed from the level of protein in the transgenic milk, the levels are preferably greater than about 10 mg/ml, more preferably greater than about 2.5 mg/ml, most preferably greater than 5 mg/ml. The foregoing molar concentration and protein levels in bovine transgenic milk will vary depending upon the molecular weight of . the particular recombinant polypeptide. A particular advantage of producing a recombinant ' polypeptide in bovine transgenic milk is that relatively large molecular weight polypeptides may be so produced which are otherwise difficult to produce in large quantities in other systems such as prokaryotic expression systems. Although any recombinant polypeptide may be produced in bovine transgenic milk according to the invention, it is generally preferred that such recombinant polypeptides have a molecular v/eight greater than about 10,000 Daltons. However, other recombinant polypeptides having molecular weights of greater than 15,000, greater than 20,000 and greater than 60,000 Daltons may also be expressed in transgenic bovine milk. For example, human lysozyme having a molecular weight of 17,000 Daltons and lactoferrin having a molecular weight of 79,000 Daltons may be readily produced in the transgenic milk of bovine species according to the disclosure of the invention. Thus, the recombinant polypeptides of the invention have a wide range of molecular weights. As a consequence, the foregoing preferred molar concentrations of recombinant polypeptides are adjusted when higher molecular v/eight recombinant polypeptides are produced. Such adjustment is made by converting the molar concentration to the amount of protein produced and adjusting the molar concentrations so that the recombinant protein level is within the following preferred concentrations. Most of the previous reports relating to the production of polypeptides in transgenic milk involve transgenic mice. The mouse, however, normally produces between 55 to 80 milligrams of protein per ml of milk. A cow, on the other hand, normally produces between 30 to 34 milligrams of protein per ml. Since exceptionally high levels of recombinant polypeptide production may adversely affect the production of endogenous milk protein and/or have adverse effects upon the mammary secretory gland, it is preferred that the recombinant polypeptide concentration be betv/een about 3 and 50% of the normal bovine milk protein concentration (i.e. , between about 1 and 17 milligrams of recombinant polypeptide per ml of transgenic milk) , more preferably between 10 to 20% (i.e. , between 3 to about 7 milligrams per ml) and most preferably between 10 and 15% (i.e., between about 3 and 5 milligrams per ml) of the normal amount of protein produced in bovine milk. Such preferred ranges also provide a preferred maximum limit to the aforementioned levels of protein produced in transgenic bovine milk. The above described linking of various DNA sequences to form the transgene of the invention are performed by standard methods known to those skilled in the art or as described herein. Once the transgene or overlapping homologous fragments encoding the transgene are constructed as described they are used to make transgenic non-human animals. Methods of introducing transgenes or overlapping transgene fragments into embryonal target cells include microinjection of the transgene into the pronuclei of fertilized oocytes or nuclei of ES cells of the non- human animal. Such methods for murine species are well known to those skilled in the art. Alternatively, the transgene may be introduced into an animal by infection of zygotes with a retrovirus containing the transgene (Jaenisch, R. (1976) Proc. Natl. Acad. Sci. USA 73:1260- 1264) . The preferred method is microinjection of the fertilized oocyte. In this preferred embodiment, the fertilized oocytes are first microinjected by standard techniques. They are thereafter cultured in vitro until a "pre-implantation embryo" is obtained. Such pre- implantation embryos preferably contain approximately 16 to 150 cells. The 16 to 32 cell stage of an embryo is commonly referred to as a morula. Those pre- implantation embryos containing more than 32 cells are commonly referred to as blastocysts. They are generally characterized as demonstrating the development of a blastocoel cavity typically at the 64 cell stage. Methods for culturing fertilized oocytes to the pre- implantation stage include those described by Gordon, et al. (1984) Methods in Enzymology 101: 414 ; Hogan, et al. (1986) in Manipulating the Mouse Embryo, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (for the mouse embryo) ; and Hammer, et al. (1985) Nature 315:680 (for rabbit and porcine embryos) Gandolfi, et al. (1987) J. Reprod. Fert. 8J.:23-28; Rexroad, et al. (1988) J. Anim. Sci. 6 . 6:947-953 (for ovine embryos) and Eyestone, W.H. et al. (1989) J. Reprod. Fert. 85:715- 720; Camous., et al. (1984) J. Reprod. Fert. 72:779-785; and Hey an, Y., et al. (1937) Theriogenology 27 : 5968 (for bovine embryos) . Such pre-implantation embryos are thereafter transferred to an appropriate female by standard methods to permit the birth of a transgenic or chimeric animal depending upon the stage of development when the transgene is introduced. As is well known, mosaic animals can be bred to form true germline transgenic animals. Since the frequency of transgene incorporation is often low, the detection of transgene integration in the pre- implantation embryo is highly desirable. In one aspect of the invention methods are provided for identifying embryos wherein transgenesis has occurred and which permit implantation of transgenic embryos to form transgenic animals. In this method, one or more cells are removed from the pre-implantation embryo. When equal division is used, the embryo is preferably not cultivated past the morula stage (32 cells) . Division of the pre-implantation embryo (reviewed by Williams et al. (1986) Theriogenology 22 . :521-531) results in two "hemi-embryos" (hemi-morula or hemi-blastocyst) one of which is capable of subsequent development after implantation into the appropriate female to develop in utero to term. Although equal division of the pre- implantation embryo is preferred, it is to be understood that such an embryo may be unequally divided either intentionally or unintentionally into two hemi-embryos which are not necessarily of equal cell number. Essentially, all that is required is that one of the embryos which is not analyzed as hereinafter described be of sufficient cell number to develop to full term in utero. In a specific embodiment, the hemi-embryo which is not analyzed as described herein, if shown to be transgenic, is used to generate a clonal population of transgenic non-human animals. One of each of the hemi-embryos formed by division of pre-implantation embryos is analyzed to determine if the transgene has been integrated into the genome of the organism. Each of the other hemi-embryos is maintained for subsequent implantation into a recipient female of the species. A preferred method for detecting transgenesis at this early stage in the embryo's development uses these hemi-embryos in connection with a unique property of the restriction endonuclease Dpn I . This enzyme recognizes the sequence GATC in double- stranded DNA but only when the adenine in each strand within this sequence is methylated at N-6. When using this preferred method, the transgene containing the sequence GATC is methylated prior to microinjection either by transferring the transgene on an appropriate plasmid through a DAM + strain of microorganisms such as E. coli MM294 or by directly methylating the transgene with dam methylase. The methylated transgene (preferably v/ithout any exogenous sequences such as plasmid vector) is then microinjected into fertilized oocytes (approximately 10 to 500 copies per pronucleus, more preferably 50 to 100 copies per pronucleus) . The fertilized oocytes so obtained are cultured in vitro to the pre-implantation stage. During this early growth and cell division phase, the genomic DNA is replicated. Accordingly, those copies of the methylated transgene integrated into the genome of the fertilized oocyte are unmethylated after replication whereas any non- integrated transgenes which may still exist after replication will remain methylated. (Lacks, S., et al. (1977) J. Mol. Biol. 114 : 153. ) This differential methylation pattern for integrated versus non-integrated transgene permits the identification of which fertilized oocytes have integrated the transgene into the genome. The identification of the pre-implantation embryos containing the integrated transgene is achieved by analyzing the DNA from each of the hemi-embryos. Such DNA is typically obtained by lysing the hemi-embryo and analyzing the thus released DNA after treatment as described by Nino iy, T. et al. (1989) Molecular Reproduction and Development 1 : 242-248. Each of the DNA samples is treated with Dpn I . Thereafter, a polymerase chain reaction (Saiki, et al. (1985) Science 230: 1350- 1354) is preformed to amplify all or part of the transgene. When the entire transgene is amplified, two extension primers each complimentary to opposite strands at opposing ends of the transgene are used for amplification. When, however, less than the entire transgene is amplified, such extension primers are chosen such that the amplified gene product spans the Dpn I site in the transgene. If Dpn I cleavage has not occurred, PCR amplification results in amplified sequences having a predetermined size whereas primer extension for those transgenes which have been cleaved will not result in exponential amplification. Generally, the Dpn I/PCR amplified DNA from the hemi- embryo is subjected to electrophoresis followed by hybridization with labeled probe complimentary to the region of the transgene between the two extension primers. This facilities the determination of the size of the amplified DNA sequences, if any, and provides an indication of whether the transgene has been integrated into the pre-implantation embryo from which the hemi- embryo was obtained (now called a "transgenic hemi- embryo") . If it has, the remaining untreated transgenic hemi-embryo is transplanted into a recipient parent. After in utero development, the transgenic non-human animal having the desired phenotype conferred by the integrated transgene is identified by an appropriate method in utero or after birth. Of course, other restriction endonucleases capable of cleaving a methylated DNA sequence but incapable of cleaving the unmethylated form of a recognition sequence may be used in the aforementioned method. The above described method using Dpn I requires that the sequence GATC be present in the transgene of interest. In those cases when such a sequence is not present, it may be readily introduced into the transgene by site directed mutagenesis (Kunkel, T.A. (1985) Proc. Natl. Acad. Sci. 82:488) or cassette mutagenesis (Wells, J.A., et al. (1985) Gene 3 . 4-315) provided such mutagenesis does not change the amino acid sequence encoded by the transgene (or causes an inconsequential change in amino acid sequence) and that any codons so generated are functional in the transgenic non-human animal of interest. The above described methods for the detection of transgenesis in pre-implantation embryos provide economical and time saving method for generating transgenic non-human animals since they significantly decrease the number of pregnancies required to produce a transgenic animal and substantially increase the likelihood that an implanted embryo will produce a transgenic non-human animal. Such methods are especially important for those animals for which very low or non-existent frequencies of transgenesis have been obtained, e.g. bovine species. In an alternate embodiment, the above described method for detecting transgenesis in pre-implantation embryos is combined with embryonic cloning steps to generate a clonal population of transgenic embryos v/hich may thereafter be implanted into recipient females to produce a clonal population of transgenic non-human animals also having the same genotype. In this regard, it is to be understood that transgenic embryos and/or non-human transgenic animals having the same "genotype" means that the genomic DNA is substantially identical between the individuals of the embryo and/or transgenic animal population. It is to be understood, however, that during mitosis various somatic mutations may occur which may produce variations in the genotype of one or more cells and/or animals. Thus, a population having the same genotype may demonstrate individual or subpopulation variations. After a hemi-embryo is identified aa a transgenic hemi- embryo, it is cloned. Such embryo cloning may be performed by several different approaches. In one cloning method, the transgenic hemi-embryo is cultured in the same or in a similar media as used to culture individual oocytes to the pre-implantation stage. The "transgenic embryo" so formed (preferably a transgenic morula) is then divided into "transgenic hemi-embryos" which can then be implanted into a recipient female to form a clonal population of two transgenic non-human animals. Alternatively, the two transgenic hemi-embryos obtained may be again cultivated to the pre-implantation stage, divided, and recultivated to the transgenic embryo stage. This procedure is repeated until the desired number of clonal transgenic embryos having the same genotype are obtained. Such transgenic embryos may then be implanted into recipient females to produce a clonal population of transgenic non-human animals. In a preferred cloning method, the transgenic embryo is cloned by nuclear transfer according to the technigues of Prather, et al. (1988) Biol. Reprod. 37:59-86; Roble, et al. (1987) J. Anim. Sci. 6_4:642-664. According to this method, nuclei of the transgenic embryo are transplanted into enucleated oocytes, each of which is thereafter cultured to the blastocyst stage. At this point, the transgenic embryos may be resubjected to another round of cloning by nuclear transplantation or may be transferred to a recipient parent for production of transgenic offspring having the same genotype. In addition to the foregoing methods for detecting early transgenesis, other methods may be used to detect transgenesis. Such methods include in utero and post partum analysis of tissue. In utero analysis is performed by several techniques. In one, transvaginal puncture of the amniotic cavity is performed under echoscopic guidance (Bowgso, et al. (1975) Bet. Res. 9j5: 124-127 ; Rumsey, et al. (1974) J. Anim. Sci. 3J3: 386-391) . This involves recovering about 15 to 20 illiliters of amniotic fluid betv/een about day 35 and day 100 of gestation. This volume of amniotic fluid contains about 1000 to 12,000 cells per ml originating from the urogenital tract, the skin and possibly the lungs of the developing embryo. Most of these cells are dead. Such cells, however, contain genomic DNA which is subjected to PCR analysis for the transgene as an indication of a successful transgenesis. Alternatively, fetal cells may be recovered by chorion puncture. This method also may be performed transvaginally and under echoscopic guidance. In this method, a needle is used to puncture the recipient animal's placenta, particularly the placentonal structures, v/hich are fixed against the vaginal wall. Such sampling may be performed around day 60 of gestation in bovine species. Chorion cells, if necessary, are separated from maternal tissue and subjected to PCR analysis for the transgene as an indication of successful transgenesis. Transgenesis may also be detected after birth. In such cases, transgene integration can be detected by taking an appropriate tissue biopsy such as from the ear or tail of the putative transgenic animal. About one to two centimeters of tail or about five to ten square millimeters of ear are obtained followed by southern blotting with a probe for the transgene according to the method of Hogan, et al. (1986) Manipulating the Mouse Embryo, Cold Spring Harbor Laboratory. Transgenesis can also be determined by using the southern blot technique with DNA obtained from other tissues. In particular, semen from a recombinant bull will be useful for identifying transgenic animals. Transgenesis may also by detected by assaying for expression of the recombinant polypeptide in a tissue, secretion (e.g., saliva) , or other body fluid. In the case where the goal is expression of a recombinant polypeptide in milk of cows it v/ill be especially useful to assay the saliva of bulls for expression levels. This is because some mammary specific promoters may also cause salivary gland expression, albeit at low levels. See, e.g., Archibald et al. (1990) Proc. Nat. Acad. Sci. USA 87Z:5178-5182. In those embodiments where a recombinant polypeptide is expressed and secreted into the milk of transgenic bovine species, the transgenic milk so obtained may be either used as is or further treated to purify the recombinant polypeptide. This depends, in part, on the recombinant polypeptide contained in the transgenic milk and the ultimate use for that protein. Thus, when the recombinant polypeptide is secreted into transgenic milk to increase the nutritional value of the bovine milk, no further purification is generally necessary. An example of such a situation involves one of the preferred embodiments wherein human lactoferrin is produced in the milk of bovine species as a supplement to control intestinal tract infections in newborn human infants and to improve iron absorption. In other situations, a partial purification may be desired to isolate a particular recombinant polypeptide for its nutritional value. Thus, for example, human lactoferrin produced in transgenic bovine milk may be partially purified by acidifying the milk to about pH 4-5 to precipitate caseins. The soluble fraction (the whey) contains the human lactoferrin v/hich is partially purified. The recombinant polypeptide contained in bovine transgenic milk may also be used in food formulations. A particularly useful food formulation comprises an infant formula containing one or more recombinant polypeptides from transgenic bovine milk which have either nutritional or other beneficial value. For example, an infant formula containing human lactoferrin from transgenic bovine milk made according to the present invention provides a bacteriostatic effect which aids in controlling diarrhea in nev/born. Similarly, recombinant polypeptides such as human casein and human lysozyme may also be generated in transgenic bovine milk to provide nutritional value. Table 2 sets forth the constituents of a typical infant formula. As indicated therein, the protein content varies between about 1.8 and 4.5 grams of protein per 100 kilocalories of formula. Thus, the total protein including recombinant polypeptide should lie between the values at least based on regulatory requirements in the United States from which the formulation in Table 2 is based. The amount of total protein including recombinant polypeptide, of course, may vary from tne foregoing depending upon the local regulations v/here the particular formula is intended to be used. TABLE Nutrient Minimum Maximum Protein (gππ) 1.8 4.5 Fat: gm 3.3 6.0 percent cai 30.0 54.0 Essential fatty acids (linoleate): percent cai 2.7 mg 300.0 Vitamins: (A) (IU) 250.0 (75 μg) 750.0 (225 iig y D (IU) 40.0 100.0 K (μg) -.0 E (IU) C.7 (with 0.7 IU/gπi .ineoleic acid) C (ascorbic acid (mg) 8.0 B, (thiamine (μg) 40.0 B (πboflavin) (μg) 60. B„ (pyπdoxine) (μg) 35.0 (wi th 15 μg/gιτ- of protein in Tormula) B,. (μg) 0.15 Niacin (μg) 250.0 Folic acid (μg) 4.0 Pantothenic acid ( g) 300.0 Biotin (μg) 1.5 1 Choi ine (mg) 7.0' Inositol (mg) 4.0' Minerals: Calcium (mg) 50.0 Phospnoru-. (mg) 25.0 Magnesium (mg) 6.0 Iron (mg) 0.15 Iodine (μg) 5.0 Zinc (mg) 0.5 Copper (μg) 60.0 Manganese (μg) 5.0 Sodium (mg) 20.0 60.0 Potassium (mg) 80.0 200.0 Chloride (mg) 55.0 150.0 'Stated per 100 ki localoπes. 'The source of protein shall be at least nutritionally equivalent to casein. Retinol equivalents. 'Required to be included in this amount only in formulas whicn are not milk-based. 'Calcium to phosphorus ratio must be no less than 1.1 nor more than 2.0. 'includes recombinant protein according to the invention or recomDinant proteins and other proteins. In addition to infant formulas, other food formulations may also be supplemented with recombinant polypeptides from transgenic bovine milk. For example, such recombinant polypeptides may be used to supplement common diet formulations. When the recombinant polypeptide is intended to be used pharmaceutically, purification methods consistent with such an application are called for. Such purification methods will depend on the particular recombinant polypeptide to be purified and are generally known to those skilled in the art. Such methods typically include a partial purification by casein fractionation followed by chromotography of the appropriate fraction containing the recombinant polypeptide. Such chromotography includes affinity chromotography, ion exchange chromotography, gel filtration and HPLC. In a specific embodiment of the invention, transgenes are provided for producing human lactoferrin in the milk of transgenic bovine species. Human lactoferrin (HLF) is a single chain glycoprotein which binds two ferric ions. Secreted by exocrine glands (Mason, et al. (1978) J. Clin. Path. 3.:316-327; Tenovuo, et al. (1986) Infect. Immun. 5L: 49-53) and polymorphonuclear neutrophil granulocytes (Mason, et al. (1969) J. Exp. Med. 130: 643-658) , this protein functions as part of a host non-specific defense system by inhibiting the growth of a diverse spectrum of bacteria. HLF exhibits a bacteriostatic effect by chelation of the available iron in the media, making this essential metal inaccessible to the invading microorganisms (Bullen, et al. (1972) Br. Med. J. 1:69-75: Griffiths, et al. (1977) Infect. Immun. 15_: 396-401 ; Spik, et al. (1978) Immunology 8_:663-671; Stuart, et al. (1984) Int. J. Biochem. 16:1043-1947) . This effect is blocked if the protein is saturated with ferric ions. Several studies suggest that HLF displays a direct bacteriocidal effect on certain microorganisms (Arnold, et al. (1980) Infect. Immun. 28_:893-898; Arnold, et al. (1977) Science 112:263-265; Arnold, et al. (1981) Infect. Immun. 12 . :655-660; Arnold, et al. (1982) Infect. Immun. 25:792-797; Bortner, et al. (1986) Infect. Immun. . 51:373-377) . The bacteriocidal effect is also inhibited by iron saturation of the protein. No mechanism for the bactericidal effect of HLF has been postulated, although it has been demonstrated that it can damage the outer membrane and alter outer membrane permeability in gram- negative bacteria (Ellison, et al. (1988) Infect. Immun. 5_6:2774-2781) . Lactoferrin is the major iron binding protein in human milk (present at a concentration of about 1.5-1.7 mg/ml) and may play a role in the absorption of iron by the small intestine. All of the iron present in breast milk is thought to be bound to hLF and is taken up at very high efficiencies compared to formula (Hide, D.W., et al. (1981) Arch. Pis. Child. 5_6:172) . It has been postulated that the high uptake of the hLF bound iron is due to a receptor in the jejunum and data has been presented suggesting existence of receptors in Rhesus monkeys (Cox, et al. (1979) BBA 588 : 120; Davidson, L.A., et al. (1985) Fed. Proc. 18 . : 901) . There is also evidence for specific lactoferrin receptors on mucosal cells of the small intestine of human adults (Cox, et al. (1979) Biochem. Biophvs. Acta. 588:120-128) . Free iron levels have been implicated in the control of the intestinal flora (Mevissen-Verhage, et al. (1985) Eur. J. Clin. Microbiol. 4:14) . Breast fed infants, compared with infants fed cow's milk, with and without added iron, were shown to have substantially reduced coliform and, elevated bifidobacteria and clostridia counts in fecal samples. In in vitro studies, human milk has been shown to have a specific inhibitory effect on E_ j _ coli (Brock, et al. (1983) Infect, and Immunit. 40: 453) . Human milk has also been shown to have a specific inhibitory effect on E ^ _ coli in small intestine due to its high content of iron binding protein, predominantly hLF (Bullen, et al. (1972) British Med. J. i:69) . Thus, the production of human lactoferrin in the milk of transgenic bovine species provides a source of human lactoferrin. Such lactoferrin may be purified from the transgenic milk for formulation purposes. Alternatively, the v/hole transgenic milk may be used, preferably after pasteurization, in either liquid or dried form. In addition, the beneficial action of human lactoferrin may be potentiated by combining the human lactoferrin or the transgenic milk containing it with human lysozyme. The human lysozyme may be simultaneously produced in the transgenic cow by introducing a second transgene simultaneously with the HLF transgene to produce a transgenic cow capable of producing more than one recombinant polypeptide in the transgenic milk. Alternatively, the transgenes may be sequentially introduced into bovine species. When such is the case, a transgenic bovine species is obtained containing one of the transgenes. Thereafter, embryonic cells, such as eggs, are obtained from the transgenic female and treated so as to incorporate the second transgene encoding the second polypeptide. Preferably, the egg is fertilized, followed by microinjection of the pronucleus of the zygote so obtained. It is to be understood that the foregoing combination of more than two recombinant polypeptides in transgenic bovine milk is not limited to the aforementioned human lactoferrin and lysozyme combination. Thus, the invention contemplates the production of transgenic bovine species and transgenic milk wherein more than one recombinant polypeptide is produced by such a transgenic animal in the transgenic milk. The complete amino acid sequence of HLF has been determined (Metz-Boutigue et al . (1984) Eur. J. Biochem. 1451 : 659-676) . HLF comprises two domains, each containing one iron-binding site and one N-linked glycosylation site. These domains shov/ homology between each other, indicative of an ancestral gene duplication and fusion event. In addition, HLF shares extensive homology with other members of the transferrin family (Metz-Boutigue, supra ; Pentecost, et al. (1987) J. Biol. Chem. 262 : 10134-10139) . Location of the amino acids involved in the iron-binding sites has been determined by X-ray crystallography (Anderson et al. (1987) Proc. Natl. Acad. Sci. 84 : 1769-1773) . A partial cDNA sequence for neutrophil HLF was published by Rado, et al. (1987) Blood 7_0: 989-993. There was a >98% agreement between the amino acid sequence deduced from the cDNA and that which was determined by direct analysis of lactoferrin from human milk. The structure of the iron-saturated and iron-free form of human lactoferrin have recently been published. (Anderson, et al., (1989) J. Mol. Biol. 209 :711-734 ; Anderson, et al. (1990) Nature: 784-787. ) As used herein, "human lactoferrin" comprises a polypeptide having the amino acid sequence substantially as described by Metz-Boutigue, et al. (1984) Eur. J. Biochem. 1451: 659-676 and as set forth in Fig. 2. It is noted, however, that an earlier partial sequence of the human lactoferrin sequence disclosed a number of discrepancies between the published sequence and that obtained herein. Specifically, the following discrepancies exist (amino acid numbering is from the sequence in Figure 1 with DNA position in parenthesis) : Amino Acid Arg Thr Gin Ser Tyr Ser between Ala and Met Cys Gin Lys Accordingly, human lactoferrin is also defined by the sequence shown in Figure 1 which combines the sequence differences obtained herein with the published sequence. The term human lactoferrin also includes allelic variations of either of these sequences or recombinant human lactoferrin variants v/herein one or more amino acids have been modified by the substitution, insertion or deletion of one or more amino acid residues. In some instances human lactoferrin may be produced in milk with all or part of a secretory signal sequence covalently attached thereto. As used herein, a "human lactoferrin DNA sequence" is a DNA sequence which encodes human lactoferrin as defined above. Such a human lactoferrin DNA sequence may be obtained from a human mammary gland cDNA library or may be derived from the human genome. Example 2 herein describes the cloning and nucleotide sequence of human lactoferrin derived from a human mammary gland cDNA library. The DNA sequence of this human lactoferrin is shown in Fig. 1 and Fig. 2 and is substantially the same as that described by Rado, et al. (1987) Blood 20:989-993. The construction of plasmids containing an expressible transgene encoding hLF is described in the examples. One of these plasmids is cGPlHLF also sometimes referred to as 16,8HLF3) contains a transgene designed for tissue-specific expression in bovine mammary secretory cells. In a second embodiment of the invention, transgenes are provided for producing human serum albumin in the milk of transgenic bovine species. Human serum albumin is a serum protein which contains 584 amino acid residues (Minghetti, et al. (1986) J. Biol. Chem. 261:6747) . It is the most abundant protein in human serum and performs two very important physiological functions. Serum albumin is responsible for about 80% of the total osmolarity of blood and it transports fatty acids between adipose tissues. Human serum albumin is used primarily to expand plasma volume by restoring osmotic pressure in the circulatory system. Currently, a heat treated serum derived hSA fraction is infused in most shock and trauma victims, including most of the patients undergoing extensive surgery. HSA is presently derived from human blood plasma as a by-product from blood fractionation processes to obtain rare blood proteins such as factor VIII and IX. The recently developed technology of producing such factors by biotechnological means, however, threatens the source of human serum albumin. As used herein "human serum albumin" comprises a polypeptide having the amino acid sequence substantially as that described by Minghetti, et al., ibid; Lawn, et al. (1981) Nucl. Acids Res. 9:6103. Also included are variations thereof including recombinant human serum albumin variants wherein one or more amino acids have been modified by the substitution, insertion or deletion of one or more amino acid residues (Minghetti, et al. (1986) J. Biol. Chem. 261: 6747-6757) . In some instances, human serum albumin may be produced in milk by expressing a transgene v/hich contains DNA encoding the secretory signal sequence of hSA. Alternatively, human serum albumin may be produced in and secreted from liver cells of a transgenic animal utilizing a completely heterologous transgene comprising human genomic DNA encoding 5' expression regulation sequences, the human serum albumin secretion signal and structural gene and 3' expression regulation sequences. As indicated in the Examples, transgenes containing this heterologous sequence were formed by in vivo homologous recombination of overlapping transgene fragments to reconstitute the hSA gene in the transgenic animal. The so formed transgenic animal produced human serum albumin in its circulatory system. As used herein, a "human serum albumin DNA sequence" is a DNA sequence v/hich encodes human serum albumin as defined above. Such a human serum albumin DNA sequence may be obtained from λHAL-HAI , XHAL-3W and XHAL-HI4 as described by Urano, et al. (1986) J. Biol. Chem. 261: 3244-3251 and Urano, et al. (1984) Gene 32:255-261 and in the Examples herein. The human serum albumin DNA sequence was cloned as described in Example 10 herein and subsequently manipulated to substitute for the human lactoferrin gene encoded in plasmid cGPlHLF (also referred to as pl6,8HLF4) . From this plasmid a transgene is obtained containing 16 kb of the 5' expression regulation sequence of the bovine αSl casein gene, human serum albumin DNA sequence and approximately 8 kb of the 3' -flanking region of the αSl casein bovine gene. This transgene is used to microinject fertilized oocytes from bovine species. After early detection of transgenesis, blastocysts containing the hSA transgene are implanted into a recipient female bovine species and brought to term. The following is presented by way of example and is not to be construed as any limitation on the scope of the invention. EXAMPLE 1 Construction of a Probe Specific for Bovine αSl Casein Sequences A. Isolation of Chromosomal DNA Placental tissue was obtained from the slaughterhouse. Surrounding connective tissue was removed and pieces of about 30 grams were quickly frozen in liquid N 2 . Chromosomal DNA was isolated as follows: 30 grams of tissue was homogenized (on ice) with 35 ml of Buffer 1 containing 300 M Sucrose; 60 mM KC1; 15 mM NaCl; 60 mM Tris.HCl pH 8.2; 0.5 mM spermidine; 0.15 mM spermine; 2 mM EDTA; 0.5 mM EGTA. 65 ml of icecold buffer 1 containing 1% NP40 was added and the mixture was incubated for five minutes on ice. After centrifugation for five minutes at 3000 xg the pellet was rinsed with buffer 1 containing 1% NP40. After repeating the centrifugation step the pellet was resuspended in 5 ml of buffer 1. 5 ml 0.5 M EDTA was quickly added. Final volume was now 15 ml. 0.15 ml of a 10% SDS solution was added. After mixing, RNAse A and TI were added to final concentrations of 0.4 mg/ml and 6 u/ml respectively. After incubation at 37°C for three hours, Proteinase K was added to a final concentration of 0.1 mg/ml. This mixture was incubated for 15 hours at 37°C. The mixture was then carefully extracted with phenol. The aqueous phase was isolated and 1/30 volume of 3M NaOAc pH 5.2 and one volume of isopropylalcohol was added. The precipitate (DNA) was rinsed with 70% ethanol and slowly dissolved in 0.5 ml of 10 mM Tris.HCl pH 8.0; 1 mM EDTA, at 4°C. B. Amplification of Sequences from the 5 '-flanking Region of the αSl-casein Gene Tv/o DNA-primers were synthesized based on the sequence published by Yu-Lee et al., (1986) Nucl . Acids Res. 14 , 1883-1902. Primer 1 was located at position-681 relative to the major transcription initiation site and had the following sequence: 5' -TCC ATG GGG GTC ACA AAG AAC TGG AC-3 ' . (Seq. ID No. : 5) Primer #2 was located at position +164 relative to the major transcription initiation site and had the following sequence: 5 ' -TGA AGC TTG CTA ACA GTA TAT CAT AGG-3 ' (Seq. ID. No. : 6) . The first eight nucleotides of this primer are not encoded by the bovine genome, but contain a Hindlll restriction site to facilitate subsequent cloning steps. These primers were annealed to the chromosomal DNA and extended in the presence of deoxynucleotides by TAQ-polymerase. After three minutes the mixture was denatured for one minute at 92°C, reannealed at 50°C for 1.5 minutes and again incubated at extension temperature (68°C) for 2 minutes. This cycle was repeated 30 times. After the last cycle DNA was checked for the presence of the expected EcoRI sites. Both the size of the fragment and the presence of EcoRI sites was as expected. The fragment was then treated with Klenow enzyme to repair any overhanging ends, treated with kinase to attach phosphate groups at the ends of the fragment, incubated at 65°C for 10 minutes to inactivate the kinase and klenow enzymes and finally digested with Hindlll. This fragment was then subcloned in pUC19 (Yanisch-Perron, et al. (1985) , Gene, 33 , 103-109) digested with Smal and Hindlll. Formal proof of the identity of this fragment was obtained by sequencing parts of this subclone (after re-cloning into M13 vector) . The determined sequence was identical to the published sequence. This probe was then used to screen a bovine genomic library to obtain clones specific for the 5 '-flanking region of the αSl-casein gene. C. Amplification of Sequences from the 3 '-flanking Region of the αSl-casein Gene A similar approach was taken as described above. Two primers were designed based on the sequence published by Stewart et al (1984) Nucl. Acids Res. 12 , 3895-3907. The 5 '-primer was located just downstream of the coding sequence starting at position 713 of the cDNA sequence. It had the following sequence: 5' -GAG GGA CTC CAC AGT TAT GG-3 ' (Seq. ID No.: 7) . The other primer was located at position 1070 of the cDNA sequence and had the following sequence: 5 ' -GCA CAC AAT TAT TTG ATA TG-3' (Seq. ID No.: 8) . These primers were annealed to the chromosomal DNA and the region between these primers was amplified as described above. The resulting fragment was -900 bp longer then expected. Sequence analysis showed that an intervening sequence of this size v/as present between nucleotide 737 and 738 of the cDNA. The amplified fragment was treated with Klenow-polymerase to repair any overhanging ends and treated with kinase to attach phosphate groups to the ends of the fragment. The fragment was then ligated into pUC19 previously cut with Smal. D. Screening of a Bovine Phage Library for αSl-casein Flanking Sequences A bovine genomic library, constructed in EMBL3 , was obtained from Dr. M. Groenen, Agricultural University Wageningen, Netherlands, and was screened in the following way. The bacteriophage particle titre was determined on Escherichia coli MB406 a permissive host strain (Stratagene Inc.) . For this, several dilutions of the phage stock were made in SM buffer (50 mJM Tris.HCl pH 7.5, 100 mM NaCl, 10 mM MgS04 , 0.01% gelatin) and mixed with 200 μl MB406 (O.D. 550 = 0.9) ; after 20 minutes at 37°C, 3 ml top agarose (Luria- Bertani medium, 0.8% agarose, 10 mM MgCl 2 ) was added and this was plated on LB plates and incubated overnight at 37°C. Approximately 600,000 phages v/ere then plated by adding the required amount of phage stock to 400 μl MB406. The subsequent plating was as described as above. The next step was transfer of the phage to nitrocellulose filters. Plates were placed at 4°C for one hour. Nitrocellulose filters (S&S) were placed on the top agarose layer and exact position was marked. After lifting, the filters were soaked for (1) 30 minutes in denaturation buffer ( 1.5M NaCl, 0.5M NaOH) ; (2) 5 minutes in neutralizing buffer (1.5MNaCl, 0.5M Tris.HCl pH 8.0) . After rinsing with 2xSSPE (360 mM NaCl, 20 mM NaH 2 P0 4 , 2 mM EDTA) , the filters were baked under vacuum at 80°C for two hours. Prehybridization of the filters was performed in a buffer containing 50% formamide, 5x Denhardt ' s solution (0.1% Ficoll, 0.1% polyvinylpydrolidone, 0.1% bovine serum albumin) , 5xSSPE, 0.1% SDS and 100 μg/ml denatured salmon sperm DNA at 42°C for two hours. Hybridization was performed in same buffer at 42°C overnight in a shaking waterbath. The probe, generated as previously described, was labelled using the Random Primed labelling kit from Boehringer Mannheim. After overnight hybridization the filters were washed three times with 2xSSC, 0.1% SDS at room temperature. Overnight exposure of Kodak XAR films was performed with amplifying screens (Dupont) at -70°C. Putative positives were plugged out of the plates and put overnight in SM buffer at 4°C. These were plated out as described above and DNA was isolated following the plate lysate method (Maniatis, T., et al. (1982) , Molecular Cloning: A Laboratory Manual, Cold Spring Harbor, N.Y.) . 5 ml SM buffer v/as added to the top agarose layer; after tv/o hours gentle shaking buffer was removed and spun at 4000 rpm at 4°C for 10 minutes. Supernatant was transferred to sterile tubes and RNase A and DNasel (both final concentration lμg/ml) was added, this was incubated at 37°C for 30 minutes. One volume of a 20% polyethyleneglycol, 2.5 M NaCl solution was added and put on ice for one hour. Centrifugation at 4000 rpm for 30 minutes at 4°C left precipitated bacteriophage particles. These were resuspended in 500 ml SM buffer, SDS (final concentration 0.1%) and EDTA (final concentration 5 mM) was added, this was incubated at 68°C for 15 minutes. Protein was removed with one phenol and one chloroform extraction step. Precipitation of phage DNA was performed with one volume isopropanol. Phage DNA was washed once with 70% ethanol and dissolved in 50 ml Tris.HCl pH 7.5, 1 mM EDTA buffer. Restriction enzyme analysis, agarose gel electrophoresis, transfer of DNA from gel to nitrocellulose filter and Southern blotting were all done according to standard procedures (Maniatis (1982) , Molecular Cloning: A Laboratorv Manual) . Hybridization with probes (described hereinafter) was performed according to the same procedure as the screening conditions described above. E. Isolation of Clones Containing 5 '-flanking Region of Bovine Sl-casein Three putative clones were identified using the probe and procedures as described above. After another round of screening, clean recombinant bacteriophage was analyzed. Digestion of cloned DNA with Sail , EcoRI and Sail/EcoRI (double digestion) and hybridization with the probe described above showed identical inserts in all three clones. The insert consisted of an 18 kb (partial Sau3A fragment excised with Sail) . Transciptional orientation in the clone was determined with hybridization of above described restriction fragments with (1) probe 1 described above, and (2) the Ncol-Nsil fragment of probe 1. This showed a region of about 16 kb upstream of transcription start. Downstream from the transcription start was another 1.9 kbp. Sequencing of part of the latter region showed the presence of exon 2 and part of intron 2 of the bovine αSl-casein gene. Additional sequencing of the region-103 —1-300 confirmed the identity of the clone. The ethidium-bromide pattern of the described restriction fragments also showed the orientation of the clone in the EMBL vector. Subsequent analysis of the clone with the following restriction enzymes (Ncol , PstI , Kpnl , BamHI , Hindlll , Bglll) resulted in the restriction map of 5' flanking region of bovine Sl-casein gene as shown in Fig. 3. F. Isolation of Clones Containing 3 '-flanking Region of Bovine αSl-casein Duplicate nitrocellulose filters from the initial phage plating used for isolating 5' clones were screened with the 3 ' αSl-casein probe using the same hybridization conditions previously described. Eight positive clones were identified after two rounds of screening. Phage DNA was prepared as described. Subsequent restriction digests with Sail , EcoRI , and Sal/EcoRI and Southern hybridization with the 3 ' αSl probe showed identical inserts in seven of the eight clones. One clone containing an 18.5 kb EcoRI insert was further analyzed with the restriction enzymes Bstell and BamHI . A restriction map of that clone is shown in Fig. 4. EXAMPLE 2 Cloning of Human Lactoferrin Gene A. Materials Restriction endonucleases, T4 ligase, and T7 polynucleotide kinase were obtained from Boehringer- Mannheim, New England Biolabs, or Bethesda Research Laboratories. Radio-isotopes were purchased from Amersham. A human mammary gland cDNA library in bacteriophage λgtll was obtained from Clontech, Inc., Palo Alto, Calif. B. Isolation of the Human Lactoferrin Gene The human mammary gland library was screened by standard plaque hybridization technique (Maniatis, et al. (1982) Molecular Cloning: A Laboratory Manual) with three synthetic oligomers. Two of the oligomers were 30-mers corresponding to the cDNA sequence of Rado et al., supra , at amino acid positions 436-445 and 682-691. The third was a 21-mer "best guess" probe based on human codon bias and coding for amino acid sequence of HLF between amino acid residues 18 and 24. Respectively, they were: (1) 5'-CTTGCTGTGGCGGTGGTTAGGAGATCAGAC-3 ' (Seq. ID No. : 9) (2) 5 '-CTCCTGGAAGCCTGTGAATTCCTCAGGAAG-3 ' (Seq. ID No. : 10) , and (3) 5 '-ACCAAGTGCTTCCAGTGGCAG-3 ' ( Seq. ID No.: 11) . The probes were radiolabeled (Crouse et al. (1983) Methods Enzymol. 101 , 78-98) and used to screen duplicate filters. Filters were washed at a final stringency of 2 X SSC, 37°C. C. Nucleotide Sequence Analysis DNA fragments were isolated by use of low-melting agarose (Crouse et al, supra) and subcloned into bacteriophase M13mpl8 or M13mpl9 (Messing et al. (1983) Methods Enzymol. 101 , 20-78) . The sequence was determined using the Sequenase enzyme (modified T7 DNA polymerase) (Tabor et al. (1987) Proc. Natl. Acad. Sci. USA 84 , 4767-4771) . All reactions were carried out according to the manufacturer's specifications (US Biochemicals) . The sequence is shown in Fig. 1. The hLF sequence v/as digested with Hindlll and EcoRI (present in the surrounding phage sequences) and subcloned into the Hindlll and EcoRI site of pUC19 to form pUS119 Lacto 4.1. This clone contained the entire coding sequence of the mature form of hLF, but lacked the complete signal sequence. EXAMPLE 3 Construction of bovine αSl-casein CAT vectors In order to determine whether the αSl casein fragments obtained in Example 1 had promoter and other properties needed to express a heterologous gene, expression plasmids were constructed containing variable amounts of 5-' and 3 '-flanking regions from the αSl-casein gene. The chloramphenicol Acetyl transferase gene (CAT) was used as a heterologous gene in these vector constructs. The CAT gene is useful to detect the expression level for a heterologous gene construct since it is not normally present in mammalian cells and confers a readily detectable enzymatic activity (see Gorman, C.N., et al. (1983) , Mol. Cell. Biol. , 2 , 1044-1051) v/hich can be quantified in the cells or animals containing an expressible gene. A. DNA sequences 681 bp of a αSl-casein promoter plus the first non- coding exon plus approximately 150 bp of the first intervening sequence (IVS) v/ere isolated from a 5'- flanking genomic clone from Example 1 by PCR amplification as an Ncol-Hindlll fragment (approximately 830 bp) . This fragment is identified as fragment 1 in Fig. 5A. The primer sequences consisted of: 5 ' -TCCATGGGGGTCACAAAGAACTGGAC-3 ' (Seq. ID No. : 12) and 5 ' -TGAAGCTTGCTAACAGTATATCATAGG-3 ' (Seq. ID No. : 13) that were designed from a sequence published by Yu-Lee et al. (1986) Nuc. Acids Res. 14 , 1883-1902. Approximately 1.6 kb (fragment 2, Fig. 5A) of αSl-casein 3 '-flanking sequence was isolated by PCR amplification from a bovine 3 '-flanking genomic clone from Example 1. This region contained the previously described splice within the 3' untranslated region of αSl-casein gene. Fragment 2 was subcloned into the Smal site of pUC19. The primer sequences consisted of: 5 ' -GAGGGACTCCACAGTTATGG-3 ' (Seq. ID No. : 14) and 5 ' -GCACACAATTATTTGATATG-3 ' (Seq. ID No. : 15) that were designed from a sequence published by Stewart et al. (1984) Nucl. Acids Res. Yλ , 3895-3907. A hybrid splicing signal comprising the 3 ' splice site of an immunoglobulin gene (Bothwell et al. (1981) , Cell , 24 , 625-637) v/as synthetically prepared and inserted into pUCIS along with unique restriction sites flanking either side to produce pMH-1. This plasmid is shown in Fig. 6. Ncol and Hindlll sites were designed such that ligation with fragment 1 from the bovine 5' genomic clone would result in the functional hybrid splice sequence. See Fig. 11. A polyadenylation sequence was obtained from SV40 virus as a BamHI-Dral fragment (fragment 3 in Fig. 5A) isolated from pRSVcat (Gorman, CM., et al. (1982) , Proc. Natl. Acad. Sci. , 21, 6777-6781) . A bacterial CAT coding sequence v/as subcloned into pUC19 as a Pstl-BamHI fragment. B. Construction of pS13'5'CAT Fragment 1 of αSl-casein promoter was subcloned into pMH-1 (Fig. 6) between the Ncol and Hindlll sites to form pMHS15' flank. The SV40 polyadenylation sequence (fragment 3) was subcloned as a BamHI-Dral fragment into pUC19 immediately 3 ' to the 3 ' αSl-casein flanking sequence (fragment 2) to form pUC19 3' UTR/SV40. This allowed for the removal of a continuous EcoRI-Sall fragment (containing the 3 '-flanking sequence and poly (A) sequence) that was subcloned into pMH-1 to derive pMHS13'UTR (Fig. 5B) v/hich was used later to construct pMHSI 3 ' UTR hlf which contains sequences encoding human lactoferrin. The EcoRI-Sall sequence (fragments 2 and 3) were subcloned into the EcoRI-Sall sites of pMHSIS' flank to form pS13 '5 ' flank. The Pstl-BamHI CAT fragment (fragment 4 in Fig. 5B) , after blunting the BamHI site with Klenow, was subcloned into pS13'5'flank (Fig. 5B) between the Pstl and Smal _ sites to form pS13'5'CAT. C. Construction of pS15'CAT The CAT fragment (fragment 4 in Fig. 5B, Pstl-BamHI) and SV40 polyadenylation fragment (fragment 3 in Fig. 5A, BamHI-Dral) were subcloned into the Pstl and Smal sites of pMHS15'flank to form pS15'CAT (Fig. 5C) . D. Assay for CAT Production Each of these CAT plasmids were transfected into human 293S cells (Graham, F.L. , et al. (1977) , J. Gen. Virol. , 36 , 59-72) by the calcium phosphate co-precipitation method (Gorman, CM., et al. (1983) , Science, 221, 551; Graham, F.L., et al. (1973) , Virology, 52, 456-467) . Cellε were harvested 44 hours after tranεfection and cell extractε were assayed for CAT activity (Gorman, CM., et al. (1982) , Mol. Cell. Biol. , 2 , 1011; deCrombrugghe, B., et al. (1973) , Nature [London], 241, 237-251, as modified by Nordeen, S.K., et al. (1987) , DNA, 6 , 173-178) . A control plasmid expressing CAT driven by the Cytomegalovirus Immediate early promoter (Boshart, M., et al. (1985) , Cell, 41, 521) was transfected into human 293 S cells to assay for tranεfected efficiency. pS13'5'CAT was expressed in these cells at a level which was approximately 30-100 fold lower than the control plasmid, but significantly higher than background. Primer extension analysis indicated that transcription had initiated predominantly in the expected region. When pS15'CAT was transfected into 293S cells, expression was also detected. EXAMPLE 4 Bovine αSl-casein/human lactoferrin expression cosmid cGPlHLF A. Construction of DNA Sequences. 16 kb of bovine αSl-casein 5' -flanking sequence from Example 1 was isolated from the bovine genomic library (phage GP1) as a Sall-Bglll fragment. The Bglll site lieε at the junction of the firεt intron and εecond exon of the αSl-caεein gene. Bovine αSl-casein signal sequence (Stewart et al. (1984) Nucl. Acids Res. 12 , 3895) was prepared from synthetic DNA synthesized on a Cylone Plus- DNA Synthesizer (Millgen/Biosearch I) and contained the entire εignal sequence plus Xhol and Cla I sites attached to the 5 '-end, and Nael to the 3 ' -end (fragment 8, Fig. 7B) . Cleavage of pUC119 Lacto 4.1 with Eael precisely opened the plaεmid at the codon for the firεt amino acid of mature hLF. Treatment with Klenow was used to fill in the overhanging 5' -end. Further digestion with AccI and EcoRI gave two fragments: (a) an Eael-AccI fragment containing the firεt 243 bp of mature hLF (fragment 5, Fig. 7C) , and (b) a contiguouε AccI-EcoRI fragment (fragment 6, Fig. 7C) of 1815 bp that contained all but five terminal codonε of the remaining coding sequence. A synthetic linker was prepared that contained the last five codons of hLF beginning at the EcoRI εite and extending for four bases beyond the stop codon. A Kpnl εite waε added to the 3 ' -end (fragment 7 in Fig. 7C) . An 8.5 kb EcoRI 3 '-fragment waε iεolated from the bovine genomic library (Fig. 4) containing εequenceε beginning juεt downεtream of the coding region of αSl-caεein and a BεtEII εite approximately 350 bp from the 5 '-end. Thiε fragment was subcloned into pMH-1 at the EcoRI site to form pMH3'E10 (Fig. 7A) . A Sail site is adjacent to the 3'-EcoRI site in pMH3'E10. B. Construction of cGPlHLF The hLF 3 '-linker (fragment 7, Fig. 7C) was subcloned into the EcoRI-Kpnl εiteε of pMH3'UTR (Fig. 7A) to produce pMH3 'UTRhLF2linker (Fig. 7A) . The εynthetic bovine αSl-caεein εignal εequence (fragment 8) waε then εubcloned into the Xhol and Smal sites of pMH3 'UTRhLF2linker to make pS13'hLFl/2L (Fig. 7B) . The two hLF coding fragments (fragments 5 and 6 in Fig. 7C) were subcloned into the Nael and EcoRI siteε of pS13'hLFl/2L (Fig. 7B) to make pS13'UTRhLF (Fig. 7C) . The large αSl-casein 3 'UTR fragment from pMH3'E10 (Fig. 7A) was iεolated aε a BstEII-Sall fragment and subcloned into the same sites of pS13'UTRhLF to form phLF3 ' 10 kb (Fig. 7D) . Cosmid cGPlHLF v/as prepared from a 3-v/ay ligation (Fig. 7F) : (1) the 16 kb 5 '-flanking sequence from phage GP1 (Example 1, Fig. 3) was modified by attaching two linker adapterε. The Sail εite at the 5 ' -end waε ligated to a Notl-Sall linker. The Bglll site at the 3 ' -end was ligated to a Bglll-Xhol linker; (2) the hLF coding region, flanked on the 5 ' -end by the αSl-casein signal sequence and on the 3 ' -end by approximately 8.5 kb of αSl-casein 3' -flanking εequence, waε iεolated as a Xhol-Sall fragment from phLF3'10 kb. The Sail site at the 5 ' -end was ligated to a Sall-NotI linker; (c) Cosmid pWE15 (Stratagene, Inc.) waε linearized v/ith NotI . Fragments from (a) , (b) , and (c) were ligated together and transfected into bacteria uεing commercial lambda packaging extracts (Stratagene, Inc.) to produce cGPlHLF. EXAMPLE 5 Bovine αSl-caεein/hLF expression plasmids. A. Construction of pS13'5'hLF The Hindlll-Sall fragment of pS13'UTRhLF was subcloned into the same sites in pMHS15' flank to form pS13'5'hLF (Fig. 7E) . This plasmid contains 681 bp of bovine αSl-casein promoter sequence, the αSl-casein/IgG hybrid intron, the αSl-caεein εignal sequence, the hLF coding region, approximately 1.6 kb of αSl-casein 3 '-flanking sequence, and the SV40 late region polyadenylation sequence. B. pS15'hLF Plasmid pS13'5'hLF (Fig. 7E) was cut with Kpnl and BamHI v/hich border the αΞl-casein 1.6 kb 3 '-flanking εequence. The larger vector fragment was purified, made blunt ended with Klenow, and self-ligated to form pS15'hLF. C. Radioimmunoaεεay for hLF An immunoglobulin-enriched fraction of ascites fluid of a monoclonal antibody againεt human lactoferrin, which doeε not croεε-react with the bovine or murine protein, waε prepared by 50% ammonium εulfate precipitation and coupled to CNBr-activated Sepharoεe 4B ( 20 mg of protein to 1 g of Sepharose) . The Sepharose beadε were suεpended (2 mg/ml) in phosphate-buffered saline (PBS; 10 mM sodium phosphate, 0.14 M NaCl containing 10 mM EDTA, 0.1% ( /v) Polylorene and 0.02% ( w /v) NaN 3 , pH 7.4. Sepharoεe suspensions (0.3 ml) were incubated for five hours at room temperature by head-over-head rotation with samples (usually 50μl) in 2-ml polystyrene tubes. Sepharoεe beadε were then waεhed with saline (five timeε with 1.5 ml) and incubated for 16 hours at room temperature with 50μl (lkBq) of 125 I-labeled-affinity- purified polyclonal rabbit anti human lactoferrin antibodies, together with 0.5 ml of PBS, 0.1% ( w /v) Tween-20. Thereafter the Sepharose was washed again with saline (four times with 1.5 ml) and bound radio activity was measured. Results were expresεed aε percent binding of the labelled antibodies added. Levels of lactoferrin in test samples v/ere expressed in nanomolar, using purified human milk lactoferrin as a εtandard (εerial dilutionε in PBS, 10 mM EDTA, 0.1% ( w /v) Tween-20. Repeated teεting of εtandard on εeparate occaεionε revealed that thiε RiA waε highly reproducible, intra- and inter assay coefficients of variation ranged from 5-10%. As little as 0.1 nanogram human lactoferrin iε eaεily detected by this RIA. D. Expression in 293S cells 293S cells were transfected with the above hLF plasmids as described (lμg of a CMV-CAT plasmid was co- tranεfected aε control for transfection efficiency) . Forty-four hours after transfection medium was removed from the cells and assayed for hLF as described εupra, RNA was iεolated aε deεcribed by Stryker, et al. (1989) EMBO J. ___ , 2669. The results can be summarized as follows: 1. Transfection efficiencies are identical for the two hLF plasmids; 2. hLF is expressed in the cells and secreted into the medium. In both cases, the levels are about 0.4μg/ml medium using about 3x 10° cells 3. The proteins behave identical to hLF in a human milk sample in a dose response assay measuring the amount of 125I- anti-lactoferrin bound as a function of the amount of εample uεed. 4. The protein haε about the εame εize ( ~ 80kD) aε in a human milk εample as judged by Western blotting. 5. The hLF RNA produced in the cellε haε the correct εize and itε level iε similar for both plasmidε aε judged by Northern - blotting. Theεe data indicate that these two expression plasmids are able to express hLF. By all standardε used so far, the protein is identical to hLF present in human milk. The heterologous signal sequence is functional in that it promotes secretion of the protein from the cellε into the medium. Further, the casein regu]atory εequenceε uεed in these plasmids are able to promote expression of a heterologouε gene. EXAMPLE 6 In vitro Maturation, Fertilization and Culture of Bovine Oocytes Immature oocytes are obtained in large quantity (400-600/day) by aspirating follicles of ovarieε obtained at abbatoirε. Immature oocytes are cultured for a period in vitro before they are competent to be fertilized. Once "matured", oocytes are fertilized with sperm which has alεo been matured, or "capacitated" in vitro. The pronuclei of the fertilized oocyte is then injected with the transgene encoding for the expresεion and εecretion of human lactoferrin. Zygotes resulting from this in vitro fertilization and microinjection are then cultured to the late morula or blastocyεt εtage (5-6 days) in medium prepared, or "conditioned" by oviductal tissue. Blastocyεts are then transferred non- εurgically to recipient cattle for the balance of gestation or analyzed for integration of the transgene as described herein. In vitro maturation (IVM) . Ovarieε are obtained immediately after εlaughter at local abbatoirε and oocyteε are recovered. Alternatively, oocyteε are obtained from living cattle by εurgical, endoεcopic, or transvaginal ultrasonic approaches. In all cases, oocytes are aspirated from ovarian follicles (2-10 mm diameter) . After washing, oocytes are placed in a maturation medium consisting of M199 supplemented with 10% fetal calf serum, and incubated for 24 hours at 39°C. Sirard et al. (1988) Biol. Reprod. 39, 546-552. In vitro fertilization (IVF) . Matured oocytes are fertilized with either fresh or thawed εperm. Sperm are prepared for fertilization by firεt obtaining a population of εperm enriched for otility by a "swim-up" separation technique (Parrish et al. (1986) Theriogenology 25, 591-600) . Motil sperm are then added to a fertilization media, consisting of a modified Tyrode ' s εolution (Parriεh et al. (1986) εupra. ) εupplemented with heparin to induce εperm capacitation (Parriεh et al. (1988) Biol. Reprod. 38 , 1171-1180) . Capacitation conεtituteε the final sperm maturation procesε which iε essential for fertilization. Sperm and oocytes are co-cultured for 18 hours. A useful feature of this IVF method is that (in the case of frozen sperm) consiεtent, repeatable resultε are obtained once optimal fertilization conditions for a particular ejaculate have been defined (Parrish et al. (1986) εupra. ) . In vitro culture (IVC) . Conventional culture systems, v/hich support development of murine, rabbit, or human ova, do not support development of bovine embryos past the 8-16 cell stage. This problem has been overcome by pre-conditioning culture media v/ith oviductal tisεue. Oviduct-conditioned medium will support bovine embryos past the 8-16 cell stage to the blaεtocyεt εtage in vitro (Eyeεtone and Firεt (1989) J. Reprod. Fert. 85 , 715-720) . Bovine embryos have proved refractory to in vitro • culture. This in part ste s from the existence of a "block" to cleavage in vitro at the 8-16 cell stage. This block may be alleviated by culturing embryos in the oviducts of rabbits (reviewed by Boland (1984) Theriogenology 21, 126-137) or sheep (Willadeen (1982) in: Mammalian Egg Transfer, (E. Adams, ed., pp. 185-210)) ; Eyestone et al. (1987) Theriogenology 28 , 1-7) . However, theεe in vivo alternatives have been leεε than ideal, in that: (1) they require the maintenance of large numbers of recipient animals, (2) they require surgery to gain accesε to the oviductε for transfer, and a second surgery (or sacrifice) to recover the embryos, (3) all transferred embryos are seldom recovered, and (4) access to embryos during culture for observation or treatment is entirely precluded. The lack of in vitro culture systemε has hampered the development of various manipulation techniques (εuch aε gene tranεfer by pronuclear injection) by preventing accumulation of baεic information of the chronology and ontogeny of bovine development, and by complicating the proceεε of culturing embryoε to a εtage compatible with non- surgical embryo transfer and cryopreservation techniqueε (e.g. , late blastocyst stages) . Bovine embryos did not yield to attempts to culture them in vitro past the 8-16 cell "block" until Camous et al. (1984) J. Reprod. Fert. 72 , 479-485 demonstrated cleavage to 216 cells when embryos were co-cultured with trophoblastic tissue. The co-culture procedure was extended to oviductal tisεue, baεed on the ability of homo- or hetero-oviducts to support development from zygote to blastocyεt. Thuε, bovine embryoε co-cultured with oviductal tiεεue, or in medium conditioned by oviductal tissue, developed from zygote to blastocyεt in vitro (Eyestone and First, (1989) J. Reprod. Fert. 35 , 715-720; Eyeεtone W.H. (1989) "Factors affecting tne development of early bovine embryos in vivo and in vitro. " Ph.D. Thesis, University of Wisconεin) . Blaεtocysts have been produced in thiε εyεte after εuperovulation and artificial inεemination, or by in vitro maturation (IVM) , and fertilization (IVF) of immature oocyteε. Blaεtocyεtε produced in thiε fashion resulted in pregnancies and live calveε after tranεfer to recipient animals. The results obtained were as follows: Step IVM IVF IVC Embryo transfer (% pregnant) Therefore, from an initial daily harvest of 500 oocytes, it is expected the approximately 55 pregnancies will reεult. Preparation of Oviduct Tissue Co-Culture and Conditioned Medium 1. Obtain bovine oviducts after slaughter or by salpingecto y. 2. Harvest lumenal tissue by scraping intact oviduct gently with a glasε slide. 3. Wash tisεue 5 timeε in 10 ml modified tyrodeε- hepeε εolution (Parrish et al. (1988) Biol. Reprod. 38 , 1171-1180) . 4. Resuspend final tissue pellet in M199 + 10% fetal calf serum at a ratio of 1 volume tiεεue:50 volumes of media. 5. Tissue suεpenεion can be uεed for embryo-co- culture. 6. Alternatively, media may be conditioned for 48h; after centrifuging the suspension, the supernatant may be used as embryo culture medium. Conditioned medium may be stored at -70°C, if desired. Conditioned medium εhould be uεed at full strength for embryo culture (no dilution) (Eyestone (1989) ibid) . EXAMPLE 7 Microinjection of hLF Transgene into Bovine Pronuclei The DNA fragment containing the hLF expression unit is excised from the vector by digestion with the appropriate restriction enzyme(s) and separated on agaroεe gelε. The fragment iε purified by electroelution, phenol and chloroform extraction and ethanol precipitation (Maniatiε et al.) . The DNA fragment iε diεεolved in and dialyzed in 10 mM triε, 0.1 mM EDTA pH 7.2 at a concentration of 1 to 2μg/ml. Microinjection needles are filled v/ith the dialyzed DNA solution. Before in vitro fertilization, cumulus cells are removed from the egg by either vortexing at maximal speed for 2 minutes or pipetting the eggs up and down several -times in a εtandard micropipet. Bovine pronuclei are injected in principle aε murine pronuclei (Hogan, B. et al. (1986) in: Manipulating the mouεe embryo, Cold Spring Harbor Laboratory) with an additional centrifugation εtep in order to viεualize the pronuclei. The injection takeε place 18-24 hourε after fertilization. The time varies depending on the bull used aε a source of semen. Different batches of εemen cauεe the nuclei to become viεible at different times. Bovine oocytes, matured and fertilized in vitro, are spun in an eppendorf tube in 1 ml of tyrodeε-hepes solution (Parriεh (1987)) at 14500 g for eight minuteε (Wall et al. (1985) Biol. Reprod. 32 , 645-651) . The embryoε are tranεferred to a drop of tyrodeε-hepes solution on a microεcope slide covered with paraffin oil. Using a hydraulic system the oocytes are fixed to the egg holder in such a way that both the pronuclei are visible (using interference-contrast or phase contrast optics) . If necessary, the oocytes are rolled to change their position on the egg holder to visualize the pronuclei. The injection needle is brought into the same sharp focus of one of the pronuclei. The needle is then advanced through the zona pellucida, cytoplaεm into the pronucleus. A εmall volume of 1-3 pl iε injected (containing 20-100 DNA copies) into the pronucleus either by using a constant flow or a pulse flow (using a switch) of DNA εolution out of the needle. Alternatively, two cell stage embryos are spun as deεcribed and the nuclei of both blaεtomerε are injected aε deεcribed. The injected embryoε are then tranεferred to a drop of co-culture medium aε deεcribed in Example 6 in order to develop to the morula or blaεtocyεt stage. EXAMPLE 8 Early Detection of Transgenesis v/ith hLF Transgene Upon the microinjection of a construct, the oocyte iε cultured. A proper site of each embryo is cleaved and subjected to lysiε (King, D. et al. (1988) Molecular Reproduction and Development 1, 57-62) , proteolyεis (Higuchi, R. , (1989) "Amplificationε (A forum for PCR Users." 2 . , 1-3) and DPNI digestion. PCR is performed as described previously (Ninomiy, T. et al. (1979) Molecular Reprod. and Devel. 1, 242-248) v/ith setε of two primers, one in αSl and the other in hLF cDNA sequence. For example, in a PCR v/here the forward primer (30mer) αSl εequence is ATG AAA CTT ATC CTC ACC TGT CTT GTG (Seq. ID No. : 16) and the reverse primer (30mer) in hLF sequence iε GGG TTT TCG AGG GTG CCC CCG AGG ATG GAT (Seq. ID No. : 17) ; 971- 1000 of Figure 1) , a 990 bp fragment will be generated. Thiε fragment contains the hitherto inactivated DpNI site by losε of adenosine-methylation, at 934 bp away from the start of the forv/ard primer. EXAMPLE 9 Production of hLF in Milk of Bovine Specieε Bovine morula developed from microinjected oocyteε are εplit according to the method of Donahue (Donahue, S. (1986) Genetic Engineering of Animals, ed. J. Warren Evans et al., Plenum) . One half of the morula is kept in culture to develop into blastocyεtε. The other half iε subjected to the DNA analysis as described in Example 8. When the result of this analysis is known, the morula kept in culture are developed into a blastocyst or as a source for nuclear transfer into enucleated zygotes. Blastocyεt tranεfer into synchronized cows is performed according to the method of Betteridge (Betteridge, K.J. (1977) in: Embryo transfer in farm animals: a review of techniques and applications) . hLF is detected in the milk of lactating transgenic offspring using the RIA of Example 5. EXAMPLE 10 Bovine αSl Casein/hSA Expression Plasmidε Three overlapping phage clones that contain the complete hSA gene are used to construct an expression vector for hSA. They are designated λHAL-HAl, XHAL-3W and λHAL- H14. They are described in Urano, et al. (1986) , _;_ Biol. Chem. , 261, 3244-3251; and Urano, et al. (1984) , Gene, 32 , 255-261. The sequence of the gene plus εome surrounding regions is publiεhed in Minghetti, et al. (1986) , J. Biol. Chem. , 261, 6747-6757. A single phage containing the complete hSA gene is conεtructed aε follows: Clone HA-1 is cut with BstEII and Ahall. The =1400 bp fragment running from poεition 1784 (in the firεt exon, juεt downεtream of the ATG) to 3181 is isolated and a synthetic linker iε attached to the BεtEII εite at the 5' end containing the firεt few amino acidε that are cut off with BstEII as well as the εequence εurrounding the ATG aε well aε a few convenient reεtriction εiteε. Thiε fragment iε called fragment #1. Clone 3W is cut with Ahall and SacI the =13.1 kb fragment running from poεition 3181 to 16322 is isolated and a synthetic linker is attached to the SacI site to facilitate cloning in phage EMBL3. This fragment is called fragment #2. Theεe two fragmentε are ligated and cloned in phage EMBL3. After identification of the correct phage, a fragment running from juεt upεtream of the BεtEII εite (where unique restriction sites have been introduced) to the SacI site are iεolated and ligated from a SacI to Sail fragment (running from position 16322 to =21200 isolated from clone H-14. These two fragments are then ligated and cloned in EMBL4. After cutting with Clal (just upεtream of the BstEII site, newly introduced) and Ba HI (just downstream of the Sail site in the phage DNA) thiε new clone yieldε a fragment containing the complete hSA gene with about 2.5 kb 3 '-flanking εequence. To conεtruct an expression vector for hSA cosmid cGPlHLF iε partially digeεted v/ith Clal and BamHI . This removes the signal sequence, the coding εequence of hLF, the 3'- UTR and poly(A) addition region of αSl-caεein as well as a small region 3' of the casein gene. This is ligated to the hSA fragment described above and the resulting cosmid iε called cGPlHSA. The expreεεion vector εo formed contains, (1) 16 kb of promoter sequenceε derived from the αSl-caεein gene, (2) the first exon and intervening sequence of thiε gene both present in GP1, (3) the signal sequence of the hSA gene the complete genomic gene coding for hSA including 2.5 kb downstream of that gene, and (4) =8 kb of 3 '-flanking εequence derived from the αSl-caεein gene. This transgene iε uεed to produce tranεgenic bovine εpecies producing hSA in their milk in a manner analogouε to that uεed to produce hLF in the milk of bovine species. EXAMPLE 11 Purification of HSA from the Milk of Bovine Species Purification of heterologouε proteinε from milk is facilitated by the fact that, following casein precipitation, those proteins, for the most part, are found in the whey fraction which is leεs contaminated than the production media used in microbial or cell- based systems. Chromatographic techniques are preferred for the purification of hSA from cow milk. This approach produces a better recovery and higher albumin purity aε well as a lower content of albumin polymers as compared with ethanol fractionation (Curling (1980) in: "Methods of Plasma Protein Fractionation", Curling, ed., Academic Preεε London, UK; Curling et al. (1982) J. Parenteral Sci. Technol. 36 , 59; Berglof et al. and Martinache et al. (1982) Joint Meeting IHS-ISBT, Budapeεt) . The εpecific tranεport role of hSA as v/ell aε itε major role in maintaining intravaεcular oεmotic pressure may also be better preεerved upon chromatographic purification (Steinbruch (1982) , Joint Meeting ISH-ISBT, Budapeεt) . The following εteps are uεed to recover hSA produced in the milk of tranεgenic cowε: 1. Precipitation of caεeinε (about 80% of milk protein) and eεsentially all the milk fat at pH 4.5 and/or by adding chymosin. The whey fraction contains the albumin; 2. Affinity-chromatography of albumin on Cibacron blue 3GA-Sepharose CL-6B (Harvey (1980) in: Methods of Plasma Protein Fractionation, op. cit.) This step serveε both to remove proteins other than albumin and to decrease the volume to be handled about 30-fold. Albumin is eluted from this matrix with 0.15 M NaCl and 20 mM sodium salicylate at pH 7.5; 3. Buffer-exchange on Sephadex G-25: deεalting into 0.025 M sodium acetate, adjustment to pH 5.2 , followed by filtration; 4. Anion-exchange chromatography on DEAE-Sepharose CL-6B. Deεorption of albumin at pH 4.5; 5. Cation-exchange chromatography on CM-Sepharoεe CL- 6B. Albumin elution v/ith 0.11 M εodium acetate, pH 5.5 and concentration of albumin at a 6% (w/v) εolution by ultrafiltration; and 6. Gel filtration on Sephacryl S-200. Fraction of high-molecular weight protein (e.g. albumin polymerε, pyrogenε) iε diεcarded. The main fraction (albumin monomers) is concentrated by ultrafiltration and formulated. It is to be noted that εtepε 3-6 are essentially identical to the method described by Curling and others (Curling (1980) op. cit.; Curling et al. (1982) op. cit.; Berglδf et al. (1982) op. cit.) for the purification of hSA from plasma. EXAMPLE 12 Tranεgenic Mice Containing the Human Serum Albumin (hSA) Transgene Generated by Homologous Recombination Three overlapping genomic hSA clones were uεed to generate the hSA gene in tranεgenic mice, λHAL-HAl, XHAL-H14 and ΛHAL-3W, are shown in Figure 8 as reported / D - by Urano, et al. (1984) , Gene , 32 , 255-261 and Urano, et al. (1986) , J. Biol. Chem. , 261 3244-3251. Briefly, a genomic library was conεtructed from a partial EcoRI digeεt of human fibroblaεt DNA. For the clones XHAL-H14 and XHAL-3W, this library was screened with 32 P-labeled human albumin genomic clones by hybridization in 1 M NaCl, 50 mM Tris-HCl (pH 8.0) , 10 mM EDTA, 0.1% SDS, 100 ug/ml of εheared εalmon εperm DNA and lOx Denhardt's solution at 65° C overnight after prehybridization in 3x SSC and lOx Denhardt ' s solution. Following hybridization, filters were washed in 0.2x SSC and 0.1% SDS at 65° C. The iεolation of the XHAL-HA1 clone was identical except that a 0.9 kb BglH-EcoRI fragment from the 5 ' end of XHAL-3W was used to screen the human fibroblast library. These three hSA phage clones v/ere used to generate three overlapping linear DNA fragments, which in composite comprised the whole HSA gene and flanking regions. The 5' moεt fragment I waε a EcoRI-EcoRI fragment isolated from λHAL-HAl; the middle fragment II waε a Acyl (=AhaII) -SacI fragment of XHAL-3W; and the 3' moεt fragment III waε a Xhol-Sall fragment of XHAL-H14 (Fig. 7) . The fragments v/ere treated with klenow DNA polymerase and dNTP' s to fill in overhanging sticky ends. In some experimentε, the blunt ended fragmentε were then treated with bacterial alkaline phosphatase to remove the 5' phosphate groups from each fragment. The overlapping DNA fragments were next concentrated then coinjected into the male pronuclei of fertilized mouse eggs according to publiεhed methodε (Hogan, et al. (1986) in "Manipulating the Mouse Embryo: A Laboratory Manual", Cold Spring Harbor Laboratory) . While the number of molecules injected varied from =25 to =100 per egg cell, the ratio of the individual fragments was approximately 1:1:1. Embryos were implanted into the uteri of pseudo pregnant female mice according to the methodε of Hogan, et al., supra. To asεay correct homologous recombination of the three overlapping fragments and integration of the nascent tranεgene into the mouse genome, genomic DNA from the newborn pups was subject to the following specific digestionε followed by Southern hybridization with HSA cDNA probeε: Bεt EH: cuts outside the HSA gene region and yields an 18 kb band if correct recombination occurred; Nco I: cuts outside the overlapping regions and yields bands of 8.0 and 9.3 kb if correct recombination occurred; Nco I + Hind III: cuts at several positionε outεide the region of overlap, indicative of the preεence of intact fragments; Hinc II: cuts in the overlapping regions, yielding several bands indicative of correct arrangement in these regions. In an initial experiment of 28 transgenic animals born, 22 had correctly recombined all three fragmentε. From 20 out of thoεe 22 animals blood was collected and assayed for the presence of hSA protein using a radio immuno aεεay. 15 out of those 20 animals showed hSA expression at levels betv/een 0.5 and 5 μg/mL. None of the animals that had no recombination or that were not transgenic εhowed any expreεεion. Uεing RNA blots, only two (the two with the highest protein level) εhowed a band. We are currently performing blotε on RNA that haε been enriched for the presence of mRNA (i.e., poly(A)+ RNA) . Uεing reverεe tranεcriptase to syntheεize cDNA, followed by PCR, we have observed a perfect relationship between the presence of RNA and protein. However, in this experiment we could not determine the size(s) of the RNA. EXAMPLE 13 Alternate Construction of Transgenes Encoding hLF This example describes the construction of two hLF transgenes wherein the first contains approximately 16 kb of αSl casein 5' expression regulation sequence (pGPlhLF (16 kb) alεo referred to aε pl6,8HLF4) and the εecond containε approximately 7.9 kb of αSl casein 5' expression regulation sequence (pGPlhLF (8 kb) also referred to as p8.8HLF4) . The overall strategy for these constructions is depicted in Fig. 9. A 1.8 kb EcoRI-BglH fragment (fragment C in Fig. 9) was iεolated from phage clone GP1. Thiε fragment runs from position -100 of the transcription start site into the εecond exon of the αSl caεein gene. The Bglll εite lieε at the junction of the first entron and second exon of the αSl casein gene. The 3' end containing the Bglll site v/as ligated to a synthetic Bglll-Clal linker and subcloned into the plasmid pUC19. The resulting plasmid is designated pEBS. Fragment B in Fig. 9 was isolated as an EcoRI fragment and cloned into the EcoRI site of pEBS. Fragment B includeε sequences from position -7500 to position -100 of the transcription start εite in the αSl caεein gene. The plaεmid εo formed iε deεignated pEB3S and containε the combination of fragments B and C is the 8.9 kb EcoRI-Clal fragment running from position -7500 to position +1400 of the transcription start site. The 8.9 kb EcoRI-Clal fragment from pEB3 , obtained by complete digeεtion with Clal and partial digeεtion with EcoRI was isolated and subcloned into EcoRI-Clal cut pKUN2 (a derivative of pKUN; Gene (1986) 4_6, 269-276 containing a NotI restriction site) to form pNE3BS. An 8.5 kb Clal-EcoRI fragment (fragment A in Fig. 9) running from position -16000 to position -7500 of the transcription start site v/as isolated from phage GP1. It was thereafter subcloned into pUC19 to form pSE. Using synthetic oligonudeotide, a unique NotI εite was introduced into the Clal site thereby deεtroying it. The reεulting plasmid is designated pNE. The insert from pNE v/as isolated as a Notl-EcoRI fragment and together v/ith the EcoRI-Clal insert from pNE3BS was ligated into the cloning vector pKUN2. The resulting plasmid pGPl (Δ2ex) contains 16 kb of αSl caεein promoter pluε the 5' end of the gene to the Bglll εite at the border of the second exon. The final plasmid (16,8HLF4) containing the transgene v/as asεembled uεing the Notl-Clal fragment from clone pGPI (Λ2ex) and the Xho-NotI fragment from clone pHLF 3' 10 kb. The structure of this transgene is the same as previously described herein. As a minor modification to this plasmid the Sail site of this plaεmid waε removed by cutting with Sail and inεerting a linker that containε a NotI site, but not a Sail site. Subsequently, a Sail site waε introduced just downstream of the hLF sequence by cutting the Kpnl site as that position adding the following linker: 5 '-CGTCGACAGTAC-3 ■ (Seq. ID No. : 18) CATGGCAGCTGT-5* (sEQ. id nO. : 19) In effect, the hLF sequence is now surrounded by two unique restriction sites (Clal and Sail) and can be replaced by any recombinant ANA sequence that has a Clal-site at the 5'- end and a Sail-site at the 3'- end. Another transgene waε conεtructed that iε identical to the foregoing except that it contains only about 8 kb of 5' αSl casein expression regulation εequence. It was constructed by taking the Notl-Clal fragment from pNE3BS and fuεing it directly into Xho-otI fragment from clone pHLF 3' 10 kb. The reεulting plaεmid waε designated pGPlhLF (7 kb) (also referred to as p8.8HLF4) . Plasmid 16,8hLF4 was modified to contain a hybrid splice εignal (αSl caεein-IgG) described in examples 3 and 5. The resulting plasmid waε deεignated 16,8hLF3 and is identical to 16,8hLF4 except for the presence of a hybrid intron versus a "natural" casein intron in the 5 '-UTR. The hLF signal sequence can also be uεed in all of the cDNA constructs disclosed herein instead of the casein signal sequence. Thiε can be done in the following way: A synthetic oligo was made that contains the complete hLF signal sequence (see Fig. 2) plus a Clal restriction εite at the 5 ' -end and an EagI restriction site at the 3 '-end. Theεe reεtriction sites also border the caεein- εignal εequence in the other plas idε (e.g. , pl6,8hLF4) . A fragment containing the hLF-cDNA surrounded by Clal and Sail sites was cloned in pGEM7 (Stratagene, Inc.) containing a Clal and Sail site. The resulting plaεmid waε digested with Clal and EagI and used as a vector to accommodate the Clal-Eagl fragment containing the hLF sequence. From the positive clones, the cDNA, with itε own εequence, was excised as a Clal-Sall fragment and inserted in Clal-Sall digested pl6,3hLF4 to generate pl6,8hLF5. Similarly, this Cla-Sal fragment containing -b U - the hLF-cDNA plus hLF signal sequence can be inserted in any hLF cDNA vector. EXAMPLE 14 Production of Recombinant Human Lactoferrin and Human Serum Albumin in the Milk of Transgenic Mice Transgenic mice v/ere generated utilizing εeveral of the transgenes identified in the examples herein. The transgenes used are identified in Tables 3 and 4. In each case, the 5' and 3' expression regulation sequenceε v/ere from the bovine αSl casein gene, the RNA εplice signal in the 5' untranslated region was either homologous from the αSl casein gene or a hybrid casein- IgG intervening sequence. The recombinant DNA in each case was derived from cDNA clones. The transgene containing 26 kb of 5' αSl casein expression regulation sequence v/as generated by in vivo homologous recombination of overlapping fragments. Briefly, a phage clone containing an approximately 14 kb Sail insert v/as identified. This insert contains about 11.5 kb of sequence upstream from the 5' caεein εequence contained in 16,3hLF and about 2.5 kb of overlapping sequence. The NotI insert from 16,8hLF4 and the Sail phage insert v/ere coinjected to produce the 26.8hLF4 mice. TABLE 3* Maximum Range expression of mean Number levels levels of recorded recorded IVS strains (uq/ml ) (μq/ml , omologous 0.0-0.8 0.0-0.1 homologous 5-36 2.5-16 omoioαous 5 0.3-3, 0.0-1. omoioαous 5 0.6-10 0.2-1.7 terologous 13 0.0-708 0.0-200 *The number in the plasmid designations before the comma represents the approximate length in kbp in the 5' sequence from the bovine αSl casein promoter/flanking region while the number after the comma represents the approximate length in kbp in the 3' flanking sequence of the αSl gene. Note the actual number of bases for the 8 kb and 16 kb promoter (5' flanking region) is 6.2 and 14.5 kDp, respectively. ^Exception: An additional pl6,8hLF4 transgenic mouse (line 145) not included in the data in Table 3 gave a maximum expression level of 224 μg/ml and a mean of 112 μg/ml. The data in Tableε 3 and 4 demonstrates that the hybrid intron + heterologous εplice acceptor εite dramatically increaεeε expreεεion levelε in a significant number of caseε (5/13) . The conεtruct 16,8hLF4 iε expressed at high level (in same range as 16,8hLF3) . However, (in mice) thiε only occurε in a εmall number of cases and 1/16 when 8,8hLF4 and 26,8hLF4 are included) . Similar resultε were obtained using a hSA cDNA. Briefly, the 16,8hSA4 transgene was constructed by digesting pl6,3hLF4 with Clal and Sail to remove the hLF cDNA sequence. hSA cDNA waε exciεed from a clone with EcoRI. A Clal εynthetic linker waε added to the 5' (upεtream) end and a Sail linker to the 3' (downεtream) end. After inεertion into the Clal/Sall digeεted 16,8hLF4 vector, 16,8hSA4 waε formed from which the NotI inεert waε exciεed and uεed for microinjection. The 16,8hSA4 conεtruct yield 9 lines. One of the 9 lines gave high level expression (100 μg/ml) ) , while the re aining 8 of 9 gave low expression (0.01-0.05 μg/ml) . This indicates that the level and the frequency of hLF expression in the mouse mammary gland are not determined by the particular cDNA used, but are an inherent characteristic of the 16,8X4 construct (i.e., the 16 kb 5' and 8 kb 3 ' flanking regions of the α-Sl casein gene combined with the heterologous IVS) . The data also εhow that 0.7 kb of 5' α-51 casein flanking εeguence doeε not drive high level expression and that 8 (6.2) , 16 (14.5) and 26 kb are more effective. In this respect, 8 kb is slightly more effective than 16 or 26 kb of 5' flanking εequence. Alεo, RNA analyεiε has shown that expression of the cDNA constructs is tissue-specific and stage-specific (i.e., expression is only obεerved in the lactating mammary gland) , that the tranεcriptε are correctly εized and that RNA and protein levels correlate. EXAMPLE 15 Generation of hLF Transgenic Cattle Transgeneεiε in the bovine εystem was obtained utilizing the pl6,8hLF4 tranεgene described in Example 13. Oocyte Maturation and Fertilization Bovine oocytes were collected by aspiration of follicles present on ovarieε obtained from εlaughterhouεeε and transported in an insulated container at 30-32°C. Oocyteε, together with follicular fluid, were aεpirated from 2-8 mm diameter follicleε and pooled into 50 ml conical tubes. Cumulus-oocyte complexes (COC) were allowed to settle into a pellet, after which the supernatant was discarded and the pellet washed in 50 ml TL-Hepes (Vander Shaws, et al. (1991) Theriogenology 35 , 288 (Abstr.) . COC, containing several intact, unexpanded cumulus cell layers, were εelected and iεolated under a diεεecting microscope at 15 x magnification, washed four times in 10 ml TL-Hepes, once in 2-3 ml TCM199+10% fetal calf serum (M199) and then paraffin oil (20 COC/droplet) . COC were incubated for 23 h in a humidified atmosphere of 5% C0 2 in air at 39°C A total of about 2500 oocytes were used. On average, two aspiration sessions occurred per week. The yield of aspirated oocytes was highly variable from day to day, with a mean daily number of about 150. Maturation and fertilization v/ere analyzed by cytological analyεiε. Maturation was defined as the breakdown of the nuclear membrane, the appearance of the first polar body and a metaphaεe plate. Oocytes were fertilized in vitro with frozen thawed-sperm obtained from three different bulls with excellent characteriεtics with respect to genetic background, field performance and ease of calving. Sperm capacitation was facilitated with heparin. Parrish, J. et al. (1986) Theriogenology 25: 591-600. Since sperm from individual bulls respond differently to specific fertilization conditions, semen from each lot was tested in advance to determine optimal heparin and εperm concentration required to maximize normal fertilization frequency and to minimize polyεpermy. Fertilization conditionε for a given bull were εelected after εcreening at heparin concentrationε of 0.0, 1.0 and 10.0 mg heparin/ml, and at 1.0, 2.0 and 4.0 x 10 6 motile sperm/ml. Since the proportion of sperm that surviveε freezing and thawing varies from bull to bull (approximately 30-60% for the bulls was uεed here) sperm preparationε were enriched for live, motile εperm by a "εwim-up" procedure (Parriεh, J. et al. Ibid) , alternatively, sperm were centrifuged through a percoll gradient. After isolation of the motile portion, sperm v/ere counted on a hemocytometer, diluted to an appropriate concentration to yield a 25-fold concentrated stock. The fertilization medium conεiεted of TALP medium (Baniεter, Bethal Biol. Reprod. 28 : 235- 247) εupplemented with 2.0-10.0 mg/ml heparin (from porcine intestinal mucosa, 177 IU/mg; Sigma) and if the cumulus waε removed prior to fertilization, ImM hypotaurine, lO M penicillamine, 20mM epinephrine and 2mM sodium metabiεulfite. Matured COC were selected on the basis of expanded cumulus masses for fertilization, washed once in 10 ml fertilization medium, and either added directly to fertilization droplets, or first stripped of their cumulus investment by gentle pipetting through a small-bore, fire-polished pipet and then added to the droplets. Finally, sperm cells were added to a final concentration of 1 x 10°-2.0 x 10°/ml. After 16-24 h, presumptive zygotes were removed from fertilization droplets. At this point, 20-30 zygotes for each experiment were fixed in 3 : 1 ethanol: acetic acid for 24 h, stained with 1% aceto-orcein (in 40% acetic acid), and examined to determine fertilization frequency (percentage of sample with 2 pronuclei and a sperm tail) . For each batch of semen, the ' in vitro ' fertilization conditions (heparin concentration and sperm number) v/ere optimized to obtain normal fertilization rates ranging from 50 to 70% as determined by the presence of two pronuclei and a εperm tail aε described above. Either one of tv/o techniques were uεed for selection of motile sperm: the εwim-up technique and centrifugation through a Percoll gradient. No εignificant differenceε in fertilization rateε between theεe methodε were recorded. The efficiencieε of theεe and the following εtepε are shown in Table 5. The remaining oocyte were then prepared for microinjection. TABLE 5 Efficiencies of the steps involved in the procesε from immature bovine oocytes to transgenic calves Microinjection. The 26 kbp casein-hLF transgene (from p 16,8hLF4) used for microinjection waε releaεed by NotI digeεtion and purified by agaroεe gel electrophoresis and electroelution. The final DNA concentration waε adjuεted to 2.5 μg/ml. Batcheε of 50 cumuluε-intact fertilized oocyteε were εtripped either aε deεcribed above or by vortexing 2 minuteε in 2ml TL-hepeε medium in a 10ml conical tube. In order to visualize the pronuclei, cumulus free oocytes were centrifuged in 1ml TL-hepes medium 8 minuteε at 14,500 x g in an Eppendorf centrifuge. Wall, R. et al. Biol. Reprod. 32 : 645-651. Microinjection waε performed eεεentially aε deεcribed by Hogan B. et al. (1985) Manipulating the Mouεe Embryo:A Laboratory Manual, Cold Spring Harbor Laboratory Preεε, Cold Spring Harbor, N.Y.. Embryo culture. Embryoε were cultured from the zygote to the compact morula or blaεtocyst stage in oviductal- tissue conditioned medium. Eyestone et al., (1991) J. Reprod. Fert. 92:59-64. Oviductε were obtained at εlaughter and transported at ambient temperature. Luminal tissue from 2-4 oviducts (1-2 cows) waε harveεted by gently εcraping intact oviductε on the outside with a glasε slide. The extruded material was -37 - washed 5 times in 10 ml TALP-Hepes and diluted in M199 to a tissue:media ratio of 1:50. Media v/ere conditioned in 50 ml "T" flaskε containing five ml of oviduct tiεεue εuεpenεion. Conditioned media frequently contained a proteinaceous precipitate after thawing, which was removed by centrifugation. Droplets were covered with paraffin oil and were incubated for 2 h to permit pH to equilibrate prior to adding zygotes. Zygotes were placed in culture dropletε within 2 h after microinjection. Initial cleavage (>2 cellε) waε aεεeεεed 42 h after adding εperm. Media were not changed during the course of incubations. Criteria for normal development consiεted of attainment of the compact morula or blaεtocyst stage. Embryo transfer. The synchronization schedule was set up so that recipients started estrous on the same day at which oocytes were aspirated from slaughterhouεe ovarieε (i.e., εtart of maturation is day 1) . Estrouε in recipient cattle v/aε synchronized with a 9-day Norgestamet (Intervert, Boxmeer, The Netherlands) treatment (adminiεtered in an ear implant according to the manufacturer) , and a 500 μg doεe of cloproεtanol given on day 7 of the Norgestamet treatment. Estrous occurred within 2-3 days after implant removal. Embryos were transferred non-εurgically to recipient heiferε 5-7 days after estrouε (1-2 embryoε/uterine horn) . Recipientε received 9-day old embryoε, at which time they have developed to the compact morula or early blastocyεt stage. These embryos are one day ahead in development compared to the stage of the estrouε cycle of the recipients. In case of two microinjection εeεεionε on εubεequent dayε, one group of recipientε waε uεed that were in εynchrony with the firεt batch of oocytes collected. Transfers of embryos that developed from oocyteε aεpirated on the day of the εtart of estrous gave better results than embryos from oocytes obtained one day later. Due to the somewhat delayed development of microinjected embryos, there appeared to be a better synchrony between the recipients and the first group of embryos. Recipients received two embryos when the quality grade (according to Linder and Wright, Theriogenology 2J3-407-416) was fair to poor and only one single embryo when the quality grade was excellent to good. Each pregnant recipient that received 2 embryos carried only one fetus to term. The overall pregnancy rate was 21%, v/hich is significantly less than the rates reported by others with non-microinjected embryoε which had developed in vivo (Linder and Wright, Ibid and Maεεy et al. (1984) Theriogenology 21:196-217) . In the experiments described here, no transfers with non- injected embryos v/ere performed. Pregnancy was determined by rectal palpation at 45 to 60 days of gestation. A total of 21 pregnancies were established (confirmed by rectal palpation 45-460 days after transfer) . During pregnancy, 2 fetuses were lost. One recipient aborted spontaneously for unknown reasonε at 7.5 monthε of gestation. The second fetus, collected at slaughter of the recipient at 3 weeks after the calculated day of parturition, was a full grown dead calf having an abnormal embryonic development called 'schistosoma reflexu ' . In both cases, no intact DNA could be isolated for analysis. Nineteen calves were born after normal pregnancies. One of these calveε died during parturition, and a εecond, 24 hourε after birth, becauεe of pneumonia following accidental inhalation of milk. A third calf, born after a pregnancy of 10 monthε and with a body weight of 70kg waε euthanized at an age of 3 weeks. Pathological analysiε indicated that the animal waε suffering from εepεis due to chronic omphalophlebitis. Tisεueε that could be analyzed from the three dead calves contained no integrated human lactoferrin (hLF) sequences. Therefore, the cause of their death is unlikely to be related to transgene integration. The remaining 16 calves are in excellent health. Structure of the transgene. In Fig. 12A, the coding sequence of the hLF cDNA is depicted by a hatched box. The position of the translational start and stop codon iε indicated. The 5' and 3' untranεlated regionε are encoded by αSl casein exons (open boxeε) . Intervening εequenceε interrupting theεe exonε are repreεented by a εingle line. The expression unit is εurrounded by flanking εequenceε derived from the bovine αSl casein gene (indicated by a double line) . Positions of restriction enzyme sites are indicated by the following symbols: R, EcoRI; A, Asp713; N, NotI. The NotI εites are not present at the indicated poεitionε in the bovine αSl caεein gene itεelf, but were introduced by εynthetic linkers. The black bar represents the position of the probe used to detect the presence of the tranεgene. Sizeε of the fragmentε (in kbp) obtained after digeεtion with EcoRI or Aεp718 are shown at the bottom. DNA analysis. DNA v/as isolated from placenta, blood and ear tiεεue from all calves. A Southern blot analysis of the extracted DNA is εhown in Fig. 12B. Ten μg of DNA was loaded per lane. Fragment size markers are in kbp (Hindlll digest of lamda DNA) are indicated on the left. Lane 1, EcoRI digested human DNA (isolated from blood) , lane 2, Eco RI digested DNA from calf #4 isolated from blood; lane 3, Asp718 digested DNA from calf #4 isolated from blood; lane 4, EcoRI digested placental DNA from calf #4; lane 5, Asp718 digeεted placental DNA from calf #4; lane 6, EcoRI digeεted DNA from calf #15 isolated from blood; lane 7, Asp718 digeεted DNA from calf #15 isolated from blood; lane 8, EcoRI digested DNA from calf #15 isolated from ear tisεue; lane 9, Aεp718 digeεted DNA from calf #15 isolated from ear tissue; lane 10, EcoRI digested placental DNA from calf #15; lane 11, Asp718 digested placental DNA from calf #15; lane 12, EcoRI digested DNA iεolated from the tail of a transgenic mouse harboring the εame construct. DNA extraction, Southern blot analysis and hybridization were performed according to standard procedures. The probe used in the Southern blotting experiment was a 758 bp EcoRV-EcoRI fragment covering the 3' part of the hLF cDNA of Figure 2. Southern blot analysis using hLF cDNA as a probe indicated that in tissues of tv/o calves (#4 and #15) transgene sequences had been integrated into the host genome. Calf #15 (a female) was mosaic for integration of the transgene. Placental tissue as poεitive, whereaε in blood and ear tiεεue no hLF εequenceε could be detected. The copy number in the placenta was 1-2. The restriction enzyme map of the tranεgene waε different from that expected baεed on the map of the casein-hLF plasmid (FIG. 12A) and based on the pattern obtained in many individual transgenic mice (data not εhown) . Apparently, a rearrangement had occurred involving a deletion of part of the DNA conεtruct. It iε not clear whether thiε rearrangement event is related to the fact that the transgene could not be detected in all tiεsues. In mice, it has been shov/n that over 30% of all transgenic animals born are mosaic. Calf #4 (a male) εhowed, in all three tissues, the same hybridization pattern that was identical to the expected one. Reεtriction digeεtionε v/ith different enzymeε indicated that head-to-tail concatamerε of intact copieε had integrated and there aε no indication of rearrangements. Copy numbers v/ere estimated by comparing the intensities of the transgenic band with bands reεulting from hybridization of the hLF probe to human DNA (FIG. 12B) . In calf #4 , between 5 and 10 copies of the transgene had integrated in all three tissues examined. An analysis of sperm producted by calf #4 detected no abnormalities. DNA was εubεequently iεolated from the εperm and analyzed for the preεence of the hLF- transgene. It appeared that the copynumber of the transgene (2-3) was the εame in sperm as in other tisεues indicating that calf #4 is not moεaic and εhould be able to tranεmit the transgene to 50% of his offεpring. EXAMPLE 16 Conεtruction of Tranεgene Cassette for Genomic Recombinant DNA The plasmids described so far all contain regions derived from the bovine αSl-casein untranscribed regionε (including intervening sequences) . When a genomic gene is to be expressed that already contains untranslated regions and intervening sequences permissive for high expression, it is preferable to uεe expreεsion cassettes where the flanking regions including the transcription initiation site of the αSl casein gene are operably linked to the untranslated regions of the gene to be expresεed. Such an expression cassette is p-16 kb,CS and waε conεtructed as follows: plasmid pSl 3 ' 5 'hLF was uεed as a template in a PCR experiment. Thiε plasmid containε 680 bp of promoter sequence of the αSl casein gene as well as its first exon. the rest of this plasmid is not relevant for thiε experiment. The upεtream primer waε located juεt upstream of the insert in the plasmid moiety (just upεtream of a NotI reεtriction εite) . Its sequence is: 5 ' -CGA CGT TGT AAA ACG ACGG-3 ' . The downstream primer was located in exon 1. Its sequence matches the first 19 bp of the exon exactly and also haε a non-hydridizing region of 17 bp containing a Clal and a Sail εite. It has the following sequence: 5 ' -ATTGTCGACTTATCGATGGGTTGATGATCAAGGTGA-3 ' The amplified fragment v/aε digested with NotI and Sail and ligated into pKUN2 (see Example 13) . The reεulting plasmid (p-680CS) therefore harbors a proximal promoter fragment from -680 to + 19, plus two restriction εiteε just downstream of those 19 bp. This plaεmid v/as digested with NotI (just upstream of - 680) and Nsil (at-280) and used as a vector to ligate to a fragment running from a NotI εite (juεt upεtream of -16 kb) to Nsil (-280) isolated from pl6,8hLF4 (Example 13) . This plasmid (p-16 kb,CS) therefore harbors a promoter fragment from =-16,000 to +19. It can be used to insert genomic geneε that carry their own UTR' ε and poly (A) -εignal . After inεertion of the genomic gene aε a Clal-Sall fragment, the αSl caεein 3'- flanking region can be inserted aε a Sall-fragment. EXAMPLE 17 Conεtruction of Tranεgene for Production of Protein C The genomic εequence of Protein C haε been publiεhed. Foεter, et al. (1985) Proc. Natl. Acad. Sci. USA 82 , 4673-4677. Thiε εequence, however, does not include the first exon which was identified through the cDNA sequence published by Beckman, et al. (1985) Nucl. Acidε Res. 13 , 5233-5247. The first exon of Protein C is located at position -1499 to -1448 in the Foster sequence. The transgene for expresεing and εecreting Protein C into the milk of bovine species is shown in Fig. 10. This transgene v/as constructed as follows. A human genomic library in EMBL-3 (Clonotech) is probed with a εequence εpecific for protein C. A purified phage DNA prep containing the complete Protein C gene iε iεolated. The phage iε iεolated from an E_;_ coli εtrain having the Dam phenotype, εuch a εtrain GM113. This results in cloned DNA v/hich is not methylated and aε εuch all Clal reεtriction εites can be cleaved. A Clal Nhel fragment running from positionε +1333 to 11483 iε iεolated. This is designated fragment I. pGEM7 (Stratogene, Inc.) is digested v/ith SphI and Smal. The region in between is replaced by the corresponding region of plasmid pKUN (Gene (1986) 4_6, 269-276) . The reεulting plaεmid iε deεignated pGEM7A and haε the following reεtriction map in the relevant region: Hindlll Clal Xbal Sail Spel Tv/o primers are synthesized, Primer GP125 has the following sequence: 5 ' - CAA ATC GAT TGA ACT TGC AGT ATC TCC ACG AC - 3 ' Clal Primer GP 126 has the following sequence: 5 ' - GGG ATC GAT CAG ATT CTG TCC CCC AT - Clal Primer GP125 has an overlap with exon 0 (position 654 to 675 of the Protein C gene) and introduces a Clal site in the 5' untranεlated region. Exon 0 iε the exon not identified by Foster, et al. Primer GP126 overlaps the region from 1344 to 1315 in the Protein C gene. This region contains a Clal site. The region between position 654 and 1344 is amplified using either human DNA or phage DNA as a template. The so amplified material is digested with Clal and cloned in vector pGEN7a to form pPCCC This vector is propagated in a dam negative strain such as GM113 and partially cut with Clal (only the plaεmidε that are cut once with Clal at position 1340 are of interest) and completely with Xbal. The Clal Nhel fragment (fragment 1) is cloned into this vector. The resultant plasmid is designated pPC Its structure is shown in Fig. 10. From this plaεmid, the Protein C tranεgene iε iεolated as a Clal-Sall fragment and ligated into pl6 kb, CΞ (See Example 15) to generate a transgene capable of expreεεing Protein C in bovine milk, thiε plaεmid iε deεignated pl6 kb,CS,PC The transgene contained within plasmid p 16 kb, CS, PC is excised with NotI and used to generate transgenic bovine species as previously described. Such transgenic animals are capable of producing protein C in their milk. EXAMPLE 18 Human Lactoferrin Transgene Formed by In Vivo Homologous Recombination: Microinjection of Two Overlapping DNA Fragments To obtain the entire hLF genomic clone, two human genomic cosmid libraries were screened using an hLF cDNA clone deεcribed herein as a probe. Of 14 clones iεolated, 2 cloneε (deεignated 13.1 and 13.2; one from each human cosmid library) contained the entire hLF gene as determined by hybridization v/ith primers specific for the first and last (17th) hLF exons and by DNA sequencing. The insert sizes of these hLF genomic clones was 42 kbp for clone 13.1 and 43 kbp for clone 13.2. Clones 13.1 and 13.2 contain 5 kbp and 13 kbp of 5' flanking sequences, respectively. The 3' flanking region of clone 13.2 is between 1 kbp and 3 kbp; clone 13.1 containε 7 kbp of additional 3' flanking εequence. The εize of the εtructural hLF gene (= introns + exons) is approximately 30 kb. The identity of the hLF clones v/as confirmed by εequencing εeveral exonε (incl. first and last) and comparing these sequences and the promoter region to the hLF cDNA sequence shown in Fig. 2. In addition, the clones v/ere tranεfected into human kidney 293 cellε and hLF expression was detected, indicating that both clones were functional. A comparison of the 13.1 and 13.2 clones (derived from independent libraries) by restriction mapping and Southern blotting revealed no differences in the corresponding regionε (i.e. in the structural hLF gene) . Southern blotting experiments revealed that the hLF gene is a single copy gene in the human genome. Figs. 13-16 illustrate the overall procedure for generating the αSl casein/genomic hLF tranεgene. The moεt 5 ' Apal εite in the εtructural hLF gene iε located in exon I, in the hLF εignal εequence. The 400 bp region immediately 5' of exon I waε εequenced. Thiε region contains the transcription initiation site of the hLF gene and a TATA-box. This region also includes a BamHI restriction site. To construct a mammary gland specific expression vector it was necessary to fuεe the 3 (6.2) kbp or 16 (14.5) kbp αSl bovine casein promoter region to the genomic hLF clone. However, the total size of εuch a conεtruct, about 50 or 60 kb (6.2 or 14.5 kb from the caεein gene promoter + 8 kb from the cosmid vector and 35-40 kb from the hLF genomic clone, i.e. , about 50-63 kb) , renders the use of conventional cloning vectors difficult. Therefore, the 8 kbp or 16 kbp αSl 5' casein promoter and flanking sequence was fused to 9 kb of the 5" region of the εtructural hLF gene (Fig. 15A) and thiε fragment waε coinjected v/ith an overlapping hLF fragment containing about 33 to 34 kbp of the 3' εequence of generic hLF clone 13.1 obtained by Clal digeεtion. See Figε. 13 and 16. The BamHI fragment (containing exon I) from clone 13.2 waε subcloned into the plasmid pUC19 (Fig. 14) . From this clone, a 8.9 kbp Apal-Sall fragment was isolated by Apal (partial digest) and Sail digestion. This fragment lacks most of the hLF signal sequence and all of the hLF 5' UTR. A synthetic sequence (Fig. 15B) repreεenting this misεing region was obtained by syntheεizing 2 complementary DNA strands (a 68-mer and a 62-mer) v/hich runs from the 5' Apal site into the downstream region from the hLF TATA-box. After annealing these primers a DNA fragment was generated which has a 5' Clal overhang and a 3' Apal overhang. Subsequent εequencing of the cbl-ApcI fragment εhowed that it has the sequence given in Fig. 15B, which differε at one poεition from the native εequence. This synthetic Clal-Apal fragment and the 8.9 kbp Apal-Sall fragment described above were ligated into p-16kbCS and into a similar plasmid, containing 8 kbp inεtead of 16 kbp of the αSl caεein promoter. Thiε yields two plasmidε, containing 16 kbp or 8 kbp of bovine αSl caεein promoter, fused to the 5' part (9 kbp) of the hLF genomic gene. See Fig. 15A. These fragments were cut out (Notl-Sall) and coinjected v/ith the 3' 33 to 34 kbp Clal fragment from hLF cosmid clone 13.1. The coinjected fragments had an overlap of 5.4 kbp. -Upon coinjection of the constructs containing the 8 kbp αSl casein promoter, 8 independent transgenic mice were identified by tail-DNA blotting. To determine if homologous recombination had occurred, chromosomal DNA (from tails of founders and offspring) was digested with Apal and analyzed by Southern blotting. The 2.7 kb Clal-Mlul fragment (see Fig. 13 or Fig. 17) that is located in the overlap was used as a probe. When homologous recombination occurred, a band of 7.5 + 0.3 = 7.8 kb is generated and detected v/ith this probe. This band is also present in human chromosomal DNA, which was used as a control in the analysis. If homologous recombination has not occurred, the probe detects bands of varying size, depending on the location of Apal εites around the site of integration. The diagnostic 7.8 kb band was detected in all 8 transgenic mouse lines, indicating that each tranεgenic mouse contained recomfoined rragments. For these 8 mouεe lines (founder no's: 936, 937, 950, 951, 982, 983, 984 and 985) , milk was collected from lactating females (founder and/or offspring) and assayed for hLF protein expresεion. The data on 7 mouεe lineε iε shown below. Mouse line ' Expression Level (max. ) (mghLF/ l) 936 4.5 937 6.0 950 0.003 951 0.010 982 5.9 983 similar to 982 and 937 on day 2 and 4 of lactation* 984 2.8 985 6.6 *: This mouse died (by accident; on day 4 of lactation. At this time, hLF expression had reached a level of 0.3 mghLF/ml. This is exactly the level found for other high expressors (e.g. lines 937, 982, 984) at this early stage of lactation. This phenomenon of gradual increase of hLF expression at the beginning of, and in particular, the first lactation haε been commonly obεerved by us in the mice generated herein. Therefore, mouse 983 is classified as a high level expresεor. The tissue-specificity of hLF expression was determined by isolating total RNA from a large number of tisεueε and analyzing for the preεence and levelε of tranεgene derived mRNA. Baεed on this analysis, hLF mRNA only occurs in the lactating mammary gland and expression is tisεue- and stage-specific. RNA levels v/ere below the threshold of detection in lines 950 and 951, but were high in high expresεing lineε and correlated with bovine αSl caεein expreεεion levels. This waε determined by Northern blot analysis of both bovine lactating mammary gland RNA and mammary gland RNA from lactating transgenic mice. A 24 bp synthetic oligomer which hybridizeε to exactly the εame sequence in the 5' UTR of bovine αSl casein RNA and in the transgene RNA was used as a probe. Expresεion levels were compared directly by quantification of the amount of labelled probe hybridized to the transgene- and αSl RNA. When a correction was made for the size difference between bovine αSl caεein (20 kD) and hLF (80 kD) , the ratio of mRNA to protein waε in the same range for bovine αSl casein and hLF. This indicates that translation and secretion of the transgene derived hLF is not impaired. The length of the hLF mRNA waε aε expected (about 2.5 kb) but in mouse line 937 a longer band (3-3.5 kb) of slightly lesε intenεity was alεo observed. The occurrence of this band may be related to the homologous recombination procesε. It remains to be determined if this RNA tranεlates into bona fine hHL. It has been suggested that casein promoters are less favorable for obtaining high level expresεion than other milk εpecific promoters. However, the present data show that this is not the case. With respect to both expreεεion level and percentage of expreεεing animalε, the tranεgeneε containing αSl casein sequenceε perform better than any other mammary gland specific transgene reported. The above data compared to those obtained with constructε containing hLF cDNA provide the following obεervation. The best cDNA expresεion vector herein (16,8hLF3) always expresses at much lower levels as compared to the genomic hLF construct. Of 13 cDNA lines generated, 8 expresεed at very low levels (1-5 μg/ml) , 5 expressed from 40 to 200 μg/ml. These relatively low levels (although high for cDNA expreεεion) aε compared to that obεerved for genomic hLF (containing the εame flanking εequenceε) indicate that genomic εequenceε produce conεiεtently higher expreεsion levels. EXAMPLE 19 Generation of Genomic Human Lactoferrin Transgeneε bv Conventional Cosmid Ligation Techniques hLF genomic transgenes have also been generated by conventional ligations in cosmids. The first construct ShLFgen is εimilar to the tranεgene generated by coinjection, but contains the 3' Clal fragment from hLF clone 13.2. The size of this fragment is about 26- 27 kb. The second construct 16hLFgen is identical to ShLFgen, but contains a larger stretch of αSl casein promoter sequences. Construction detail: The Motl-Mlul fragment from the construct depicted in Fig. ISA (referred to as 8hLFgen9k) was used to prepare the ShLFgen construct. This Notl-Mlul fragment contains the εynthetic Clal-Apal fragment depicted in Fig. 15B. This εynthetic sequence contains 24 bp of the hLF 5 ' -UTR and encodes for most of the hLF εignal εequence (εee Fig. 15C) . Thiε Notl-Mlul v/as ligated with the 3' Mlul- Clal fragment from clone 13.2 and a Clal-NotI linker aε εhown in Fig. 17. The cloning vector v/as cosmid pWE15 cut v/ith NotI, from which tne internal Clal and Sail εiteε had been deleted. The firεt intron of the hLF gene iε located 4 bp downεtream of the Apal site in the signal sequence. As a result, the DNA sequence encoding the 19 aa εignal sequence is partly located in exon 1 (43 bp, encoding 14 aa and 1 codon partially) and in exon 2 (the first 14 bp, encoding 4 aa and 1 codon partially) . The exact position of hLF intron 1 was determined by DNA sequencing and comparing the genomic sequence to the hLF cDNA sequence. The sequence upεtream of the tranεlation initiation εite (355 bp, containing the hLF 5' UTR and 5' flanking region) was also sequenced. The hLF transcription initiation site waε not included in the genomic hLF conεtructε aε εhown. Instead, they contain the bovine αSl caεein gene tranεcription initiation εite. Although the exact poεition of the hLF 'cap' site has not been determined, it is probably located about 30_bp downstream of the 'TATA' box, as is the case for the vaεt majority of eukaryotic genes. In addition, for the mouse LF gene the transcription initiation εite haε been mapped (Shirεat, et al . (1992) Gene 110, 229-234; Liu and Teng (1991) J. of Biol. Chem. 32 f 21880-21885) . On the baεis of homology between the LF and hLF 5' UTR, it is concluded that genomic hLF constructs herein do not contain the hLF transcription initiation site. The cDNA contains a Thr codon (ACA) at aa position 130 (see Fig. 2). The corresponding region in genomic hLF cloneε 13.1 and 13.2 (exon 4, plus parts of intron 3 and 4) have been sequenced. Theεe clones contain the sequence ATA, which encodes isoleucine. The cDNA also contains a Cys codon (TGC) at position 404 (see Fig. 2) . In hLF clones 13.1 and 13.2 this is a GGC, encoding glycine. By using the Notl-Mlul fragment from 16hLFgen9k instead of from 8hLFgen9k, 16hLFgen was generated. Construction of 8hLFqen37: The 5' Notl-Mlul fragment from the conεtruct depicted in Fig. 15A (called 8hLFqen9k) waε ligated to the 3' Mlul-Clal fragment from clone 13.1, combined with a Clal-NotI linker (compare Fig. 17: read 13.1 instead of 13.2) . The cloning vector was cosmid pWE15, from which the internal Clal and Sail siteε had been deleted, cut with NotI. Prior to microinjection, vector sequences were removed via NotI digestion. All constructs were cut rrom tne vector using NotI, and microinjected. Expression data: Three mice containing ShLFgen and 5 mice containing 16hLFgen were generated. Preliminary expression date in milk are as follows: ND = not done SUBSTITUTE SHEET EXAMPLE 20 Bovine --LG/Human Lactoferrin Transgenes The bovine /_.LG-promoter (beta-lactoglobulin) was used to construct a transgene encoding for the expression of hLF. Briefly, the αSl promoter in the genomic hLF constructs 8hLFgen and 8hLFgen37 were replaced with the bovine βLG-promoter. The resulting constructε are referred to aε βLG-hLFgen and 0LG-hLFgen37. The overall εtrategy for these constructions are depicted in Figs. 18-20. Isolation of the bovine <3LG-promoter. The charon 28 phage clone λβLG-13 , described by Silva et al., (1990) Nucl. Acids Res. 18:3051, was obtained from Dr. Carl A. Batt. This clone was isolated from a bovine genomic library by screening with a LG cDNA probe. It containε the structural jδLG gene and about 8 kb of 5 ' flanking region. From this clone, a 4.3 kb EcoRI fragment was isolated and εubcloned into plasmid pKUN5 using standard procedures (see Fig. 18) . From this plasmid, a 3.2 kb Notl-SacI fragment was isolated. The NotI site was derived from the polylinker of the cloning vector. The SacI site lieε 15 bp downεtream of the BLG tranεcription initiation εite. A PvuII εite iε located five bp upstream of the translation initiation site. A fragment representing the region between the SacI and PvuII siteε (including these εites) was generated by syntheεizing and annealing the 30-mer and 37-mer DNA oligomers depicted in Fig. 18. This fragment also contains a Clal and a Sail site directly downstream of the PvuII site (Fig. 18) . The 3.2 kb Notl-SacI fragment and the εynthetic Sacl-Sall fragment were ligated into a pKUN plaεmid (pKUNldeltaC) , from which the internal Clal site had previously been removed by cutting with Clal and subεequent treatment of the cut vector with Klenow enzyme. Thiε ligation reεulted in plaεmid pBLG3.2. The 734 bp region directly upstream of the translation initiation site was εequenced and compared to the correεponding region of the publiεhed sequence of the εheep BLG promoter (εee Fig. 24) . Overall homology was 91%, indicating that the sheep- and bovine BLG-pro oters are very similar. Generation of βLG-hLF constructs: The 8.9 Clal-Sall fragment from construct 8hLFgen9k (Example 15A) was isolated and cloned into p/3LG3.2 after cutting this vector with Clal and Sail. Thiε ligation reεulted in conεtruct pβLGhLFgen9k (Fig. 19) . From this construct the 9.4 kb Notl-Mlul fragment was isolated and, together with the 23-24 kb MluI-NotI fragment isolated from ShLFgen, ligated into a NotI cut pWE15 cosmid, resulting in p LG-hLFgen (Fig. 19) . The 34 kb NotI insert was isolated from the cosmid by NotI digestion and microinjected following standard procedures. For the generation of pβLG-hLFgen37 the 9.4 kb Notl-Mlul fragment from p LGhLFgen9k was ligated with the 30 kb 3' Mlul-Clal fragment from hLF clone 13.1, combined with a Clal-NotI linker into a NotI cut pWE15 cosmid vector. The βLG-hLFgen insert was isolated and microinjected following standard procedure. Expression data: βLG-hLFgen (the shorter of the 2 constructε) was injected and 7 independent mouse lines were produced. Expression data for hLF product in milk is available for the following lines: SUBSTITUTE SHEET EXAMPLE 2 1 Isolation of a Genomic hLF Fragment Containing Both the Structural Gene and the hLF Promoter HLF is normally expressed at relatively high levels (1- 2 mg/ml) in human milk. To determine whether the hLF promoter can drive high level hLF expresεion in the milk of transgenic animals, the intact hLF gene under control of its own promoter was microinjected using standard procedures. Conεtruction detailε: Two important pointε determined the construction route. Since the cosmid vector C2RB (Fig. 13) containing the genomic hLF cloneε doeε not contain unique restriction siteε flanking the hLF inεert, the intact inεert could not be iεolated directly from thiε cosmid. It was deεirable to include all 5' and 3' flanking εequences preεent in hLF clones 13.1 and 13.2 into the transgene. Since clone 13.2 (Fig. 13) contains the moεt 5' flanking εequenceε (13 kb) and clone 13.1 the moεt 3' flanking sequences (7 kb more than 13.2) , the 5' part of 13.2 was combined with the 3' part of 13.1. The cosmid 13.2 waε linearized at the Pvul εite 0.5 to 0.8 kb upεtream of the 5' region of the hLF inεert (Fig. 20) and subεequently treated with the exonucleaεe Bal31, thereby removing approximately l kb of coεmid and 0.2 to 0.5 of 5' hLF εequence. Subεequently, the DNA was treated with T4 polymerase to create blunt ends and cut with Mlul. The approximately 19 kb (12.5 5' flanking sequenceε + 6.2 kb hLF gene) blunt end-MluI cut plasmid vector (pKUN6deltaCla, Smal-Mlul), reεulted in plasmid phLF5'M gene 37. This plaεmid containε a NotI εite directly 5' of the Smal εite. From thiε plaεmid, the 19 kb Notl-Mlul fragment waε isolated and ligated with the 30 kb MluI-NotI 3' fragment from conεtruct 8hLFgen37 into a NotI cut pWE15 cosmid, resulting in p5'hLFgen37 (Fig. 20) . The 49 kb NotI insert was isolated and microinjected following standard procedures. Expression data on construct p5 'hlLFqen37 : Eight independent founder mice have been generated for the p5'hLFgen37 construct; expression data are available for 6 lines. ND = not done EXAMPLE 22 Generation of Mammary Gland Specific hLZ Expression Cassettes The structure and sequence of the human lysozyme gene has been described (Peters, et al. (1989) Eur. J. Biochem 182:507-516.. The structural hLZ gene contains 4 exons and is 5.3 kb in size. Using a 91-mer synthetic DNA sequence complementary to part of exon 2 of the hLZ gene as a probe, several s υ BS τrτυτe SHEET independent hLZ clones were isolated from a human genomic phage library. The clone λ7.2.1 contains 14 kb insert comprising 8.7 kb of 5' flanking sequences and 5.3 kb of the genomic hLZ gene. Exon 4 is only partly included: clone λ7.2.1 εtopε at one of the Sau3A sites at position 5333 and 5350 (numbering according to Peters, et al., op. cit.) . The region downstream of position 5333/5350 (532 or 549 bp of exon 4 sequences) is misεing. Theεe εequenceε are non-coding and repreεent part of the 3' UTR of the hLZ gene. All hLZ coding sequences are present in λ7.2.1. Expreεεion Vector 16,8hLZ The deεign of expreεεion vector 16,8hLZ, shown in Fig. 21, is aε followε. The 5' flanking region (including the promoter) of the hLZ gene waε removed and replaced with the bovine αSl caεein gene promoter by εubcloning into the plasmid p-16kbCS which is deεcribed in Example 16. The fuεion εite is located in the 5' UTR of the hLZ gene (exon 1) , such that in addition to 23 bp of casein 5' UTR most of the hLZ 5' UTR is preεent. All coding sequences in this construct, including the signal sequence, are derived from hLZ clone λ7.2.1 (Fig. 23A) . The 3 'UTR of the hLZ gene in clone λ7.2.1 was fused to the 3 'UTR + flanking region of the bovine αSl casein gene described previously. The resulting 3'UTR of construct 16,8hLZ is therefore derived partly from the hLZ gene (exon 4, running from bp 4761 to bp 5333/5350) and partly (including par of exon 8 and all of exon 9) from the bovine αSl casein gene. The 3' flanking region (8 kb) iε derived entirely from the bovine αSl casein gene. Conεtruction detailε for 16,8hLZ: 16,hLZ: The 6 bp directly 5 ' to the AUG codon in hLZ exon 1 conεtitute a Hindi site. A Sail phage polylinker site is located directly 3' of the λ7.2.1 inεert. These sites were used to iεolate a 5.3 kb HincII-Sall insert (Fig. 23) . The εequence running from +3 (relative to the tranεcription initiation site at +1) to the Hindi site, was εyntheεized by annealing the 31-mer and 35-mer depicted in Fig. 23A. The reεulting εynthetic DNA fragment has artificial 5' KpnI-HincII fragment and the 5.3 kb HincII-Sall fragment were εubcloned into a Kpnl- Sall cut pKUN-1 plaεmid (Fig. 23A) . From the resulting 9.3 kb plaεmid (pKHLyε3 ' 5.3 the 5.3 kb Clal-Sall fragment waε iεolated and εubcloned into a Cla-Sall cut p-0.7kbCS plaεmid (the equivalent of p-16CS but containing leεε 5' flanking sequenceε) , resulting in pKhLZ0.7. The 8 kb bovine αSl casein gene EcoRI fragment containing the 3' casein UTR and ca 6.6 kb of flanking sequences, waε iεolated from plasmid pKE3 'E10 (described previously) as an 8 kb 5 ' -XhoI-SalI-3 ' fragment (Fig. 23B) . Thiε fragment waε subcloned into the Sail site of pKhLZ0.7, resulting in pO.7 , 8hLZ. After thiε, the Sail site of p0.7,8hLZ was replaced with a NotI site by insertion of linker S1/S2 (Fig. 23C) , yielding plasmid p0.7,8hLZNt (Fig. 23D) . From this plasmid, the 13.3 kb Clal-NotI fragment was isolated and ligated with the 14.5 kn Notl-Clal fragment from p-16CS into a NotI cut pWE15 cosmid (Fig. 23E) . From the resulting construct (named 16,8hLZ in Fig. 23E) the 27.8 kb NotI insert was isolated, purified and microinjected into murine and bovine zygotes following standard procedures. Expression Vector 16,8hLZ3 The design of expreεεion vector 16,8hLZ3, εhown in Fig. 22, iε aε follows. Previously described expression vector 16,8hLF3 was uεed in the conεtruction of 16,8hLZ3. The vector 16,8hLZ3 containε not only the bovine αSl caεein gene promoter, but alεo the complete firεt exon and part of the first intron of the bovine αSl gene. In addition, it contains part of the first intron plus the splice acceptor site of an immunoglobulin gene. The signal εequence and part of the 3 ' UTR and the complete 3 ' flanking region are also derived from the bovine αSl casein gene. The hLF cDNA and the αSl casein signal εequence are exciεed from this vector by Clal-Sall double digestion. The Clal site iε located 5 bp 5 ' to the tranεlation initiation codon. An 5.3 kb Clal-Sall hLZ fragment waε isolated from plasmid pKhLZ0.7 and subcloned into a Clal-Sall cut 16,8hLF3 vector from which the hLF cDNA had been removed by Clal-Sall double digestion. The 16,8hLZ expression cassette vector sequence was removed by NotI digeεtion, εubsequently purified according to standard procedures and microinjected into mouse zygoteε. Expreεεion data: Construct 16,8hLZ: Seven transgenic mice were generated for construct 16,8hLZ. Expression data are available for 6 independent mouse lines (data from lactating offspring, using our standard hLZ assay on milk samples) . - 1 1 - _ The above data illustrates that 16,8hLZ expresses at relatively nign levels. In r-u-nan milk, hLZ levels are only 50 μg/πil (max] . Since hLZ is a 15 kD protein, a level of 0.26 mg/ml hLZ compares to ~ 1.3 mg/ml of hLF (hLF is 80 kD) . Construct 16.8hLZ3: Four independent transgenic mice were generated for covalent 16,8hLZ3. The following expression data are available from mouse lines 905 and 907. Mouse line Expression (ug/ml) (max) 905 475 907 10 The data show that 16,8hLZ3 can be expressed at relatively high levels (0.36 mg/ml compares to - 1.8 mg/ml hLF) . However, as also shown, 16,8hLZ3 does not always express at high levels. Although the number of mice analyzed is very low, constructs 16,8hLZ and 16,8hLZ3 seem to behave more or less similar with regard to frequency of expression and expression levels. It should be noted, however, that another 7 lines of mice transgenic for 16,8hLZ also contain the 16,8hLF3 construct. (See below.) None of these lines expressed SUBSTITUTE SHEET as high aε 0.36 mg/ml. Therefore, l6,8hLZ3 appears to be a more efficient conεtruct then 16,8hLZ. Thiε could be caused by the heterologous splice site (which doeε enhance hLF cDNA expreεεion levels) . EXAMPLE 23 Transgenic Mice Containing Transgenes Encoding Genomic hLZ and hLF cDNA Coinjection of 16,8hLF3 and 16,8hLZ To assess the feasibility of simultaneously expressing hLF and hLZ in the milk of transgenic animals, the appropriate isolated and purified 16,8hLF3 and 16,8hLZ constructs were coinjected into murine zygotes. Seven independent mouse lines transgenic for both constructε were generated. The expreεεion data available for each line are aε follows: Concluεionε: Only line 649 (1/7) expresses hLZ at relatively high levels. Line 649 and mouse line 660 (2/7) expreεε high levelε of hLF. Comparison to data obtained from single construct injections: For 16,8hLZ: The hLZ expression level of mouse line 649, coinjected with the 16,8hLF3 and 16,8hLZ expression cassettes is comparable to that of line 661 injected only with 16,8hLZ. In most caεeε, high level expreεεion of hLZ iε not obtained upon coinjection (1/7: high expreεεion (line 649) ; 2/7 (650 and 660) : intermediate-low expression; 4/7: low expression) . Upon injection of single hLZ transgene, similar data are obtained (1/4: high expression (line 661) ; 1/4: intermediate; 2/4: low expression) . Therefore, behavior of the 16,8hLZ transgene is not meaεurably influenced by the presence of the 16,8hLF3 transgene. Note that none of the 7 lines expreεεed aε high as line 905 (construct 16,8hLZ3) , although the level of 649 is in the same range. In concluεion, theεe conεtructε can be expressed at relatively high levels (0.2-0.5 mg/ml range) with approximately 20-25 % of the resulting transgenic mice expressing at these high levels (3/13; 7 coinjections + 6 single inj . ) . Also coinjection with 16,8hLF3 does not appear to influence expression of 16,8hLZ. For 16,8hLF3: The single injection of 16,8hLF3 resulted in 13 independent transgenic mouse lineε which can be divided into 2 groups: (1) the low expressors which produced levels are from 0.1 to 5 μg/ml (8/13) and (2) the high expressors which produced levels from 40 tc 200 μg/ml (5/13) . Of the mice having the coinjected fragments, 2/7 express at high levels. Thiε iε εimilar to the frequency of high level expression observed upon injection of one fragment (5/13) . However, both 16, 8hLF3/16, 8hLZ mice lines (649 and 660) express hLF at much higher levels than observed previously. This indicates that the presence of the hLZ construct εtimulates expression of the 16,8hLF3 construct. In line 649, the high hLF levels are accompanied by high hLZ levelε. For line 660, thiε is less clear as hLZ levels are intermediate. However, aε illustrated below, RNA analysiε reveals that the 16,8hLZ transgene in line 660 is transcriptionally at least as active as the hLF transgene. Reεults from expresεion analvsis at the mRNA level: Northern blot analysis was performed on both bovine lactating mammary gland total RNA and mammary gland total RNA from lactating transgenic mice (including mice tranεgenic for genomic hLF, 16,8hLF3 and 16,8hLF3 + 16,8hLZ) . A 24 bp εynthetic oligomer which hybridizes to exactly the same εequence in the 5' UTR of bovine αSl caεein RNA and in all transgene derived RNA was used as a probe. Expresεion levelε were compared directly by quantification of the amount of labelled probe hybridized to the tranεgene- and bovine αSl RNA. It appeared that the ratio of hLZ- to hLF-mRNA and of hLZ- to bovine αSl mRNA waε much higher than expected from the hLZ- and hLF protein levels. For example, line 649 expressed -0.2 mg/ml of hLZ and -1-2 mg/ml of hLF. After correcting for protein size (factor 5) , hLZ and hLF mRNA levels are expected to be within the same range, with hLF levels about 2-fold higher than hLZ RNA levels. However, in line 649 hLZ mRNA levels were 20- fold higher than the hLF mRNA levels. Comparative RNA analysis of lines 650, 661, 662 and bovine mammary gland RNA confirmed these data. It can therefore be concluded that tranεcriptionally, very high levels of hLZ expression are obtained using genomic hLZ εequenceε and the bovine αSl caεein gene baεed expreεεion εyεte of the invention. The genomic hLZ conεtructs are transcribed at much higher levels than the hLF cDNA constructs, and expressed in the same range as the genomic hLF transgeneε. To compare the performance of different hLF and hLZ transgenes at the translational level, a 20-fold correction should be made. The transcriptional activity of hLZ tranεgeneε expreεεing at 0.25 mg/ml iε comparable to a protein level of 5 mg/ml, a level of 50 μg/ml equivalent to 1 mg/ml. In addition, mouεe line 649 hLZ mRNA levelε exceeded bovine αSl mRNA levels - which had been 10-fold diluted - several fold. Since bovine αS - caεein iε expreεεed at ~ 12 mg/ml (and iε of similar size as hLZ) , theεe hLZ RNA levels would be equivalent to an expresεion level of several mg/ml. EXAMPLE 24 Generation of 16,8 A hLZ: Construct 16,8 A hLZ3 iε a derivative of 16,8 hLZ3. In 16.8 A hLZ3 the hLZ 5' UTR εequences and the hLZ εignal εequence have been replaced with the corresponding εequenceε from the bovine αSl-casein gene. Construct 16,A hLZ3 iε a derivative of 16,8 A hLZ3. In 16.A hLZ3 the bovine αSl-caεein gene 3' UTR and flanking sequences have been replaced with the hLZ3 ' UTR and 4.5 kb of hLZ3" flanking sequenceε. Conεtruction details: Vector p07.8hLZ (Fig. 23B) was digested with Clal and Sail. The 4.7 kb fragment (comprising 0.7 kb of the αSl-casein 5' flanking sequenceε and the plaεmid vector) waε isolated and ligated to linker GP 278/279 (Fig. 25) . This DNA εequence compriεeε part of the bovine αSl-casein 5' UTR, the complete bovine αSl-casein signal sequence and 25 bp of hLZ sequence, encoding the N-terminal region of adult hLZ. The ligation product was isolated and ligated to a 5.3 kb Ball-Sail fragment from pKHLys3'5.3 (which is depicted in Fig. 23A) . The reεulting constructs iε p0.7AhLZΔ3'. From thiε conεtruct the 5.3 kb Clal-Sall fragment waε iεolated and inserted into a Clal-Sall vector, derived from pl6,8hLF3 (also uεed in construction of 16,8 hLZ3) . The resulting conεtruct is designated pl6,8A hLZ3 (Fig. 26) . For construction of 16,A hLZ3 the vector p0.7AhLZΔ3' was digested with Xbal and Sail, and a Xbal- Notl-Sall linker was inserted (Fig. 27) . This vector was linearized with Xbal, and the 6.5 kb Xbal fragment from XHLYS1 (described by Peterε et al., Eur. J. Biochem. 182, 507-516, 1989) was inserted in the sense orientation. This resulted in vector p0.7AhLZ. From this vector, the 9.8 kb Clal-NotI hLZ fragment was isolated and, together with the 14.5 kb Notl-Clal fragment from pl6.8hLZ3, inεerted into the NotI digeεted pWE15 coεmid vector. In both caεeε, the tranεgene without plaεmid sequences was iεolated as a NotI fragment (16, 8A hLZ3; 27.8 kb; 16,AhLZ3; 24.3 kb) , purified and microinjected into fertilized mouse oocytes following standard procedures. Four independent transgenic founder mice have been generated with construct 16,8 A hLZ3 and 6 mice were generated with construct 16 A hLZ3.Preliminary expression data: Mouse line max. hLZ expresεion (μg/ml in milk) 16,8 A hLZ3: 1711 56 1783 20 16 A hLZ3: 1806 267 1809 2400 Fro these results it can be concluded that construct 16 A hLZ3 yields much higher expression levels than any other hLZ construct tested. Preliminary quantitative Northern blotting data combined with data on hLZ protein expresεion levels indicate that the discrepancy between RNA and protein levels as observed for constructs 16,8hLZ and 16,8hLZ3 does not occur with construct 16 A hLZ3. EXAMPLE 25 Transmission experiments with "Calf #4 Three heifers were super-ovulated uεing normal procedures used in cattle breeding (described in Diekman, S.J. et al. (1989) Theriogenology 31:473-487) . These animals were subεequently inεeminated with εperm from "calf #4" as described in Example 15. Calf #4 was judged to be transgenic as described in Example 15. The insemination resulted in two pregnancies. These two animals were slaughtered four weeks after insemination and the embryos recovered from the uterus. Total DNA was isolated from these embryos following procedures as described in Maniatis et al. (1982) , digested with EcoRI, and analyzed by "Southern Blot technique". The blot was hybridized to a probe specific for the hLF gene (same protocol aε in example 15) . Of the 12 embryos recovered 6 (50%) showed an hLF-specific band. In all cases the band was of the expected size and intensity. This indicates that: (a) the transgene transmitε with an efficiency of appr. 50% (b) the copy number is the εame as in the founder (~3) (c) no gross rearrangements have occurred during transmission Of the six transgenic embryoε, five were male and one v/as female according to a PCR-analyεis with primers specific for a bovine Y-chromosome repeat. These data demonstrate that the tranεgene can be tranεmitted to both maleε and females and has not integrated in the Y- chromosome. The sequences of the Y-chromosome εpecific primers are: Forward primer: 5 ' -GGA TCC GAG ACA CAG AAC AGG-3 ' Reverse primer: 5 ' -GCT AAT CCA TCC ATC CTA TAG-3 ' EXAMPLE 26 Expreεsion of recombinant proteins in saliva of calves Ten animals were born from oocytes co-injected with the hLF transgene (as described in Example 18) and a hLZ transgene (16,8hLZ; described in Example 22) . None of these animals appeared transgenic as judged by Southern Blot, but four of them (all males) were judged to be mosaic based on PCR with 0.5 μg DNA from blood and ear. Primers for this PCR-experiment were located in exon 8 of the hLF gene. The sequences of the primers are 5'-TTT GGA AAG GAC AAG TCA CCG-3' and 5' -CTC ACT TTT CCT CAA GTT CTG-3 ' All ten animals were tested for hLF and hLZ expression in saliva. Epithelial cells in the salivary gland are structurally and functionally εimilar to εuch cells in the mammary gland, and some milk protein geneε may also be expreεεed in εalivary gland (albeit at much lower levels than in mammary gland) . Approximately 2 ml of saliva was collected from the mouth of the animal and levelε of protein were determined in these samples using a radioimmunoassay as described in Example 5. Of the ten animalε, three εhowed expreεεion of hLF above the lower limit of detection. All three animalε were part of the group of four animalε judged to be oεaic. Expression levels were as follows: animal sample 1 (ng/ml) sample 2 (ng/ml) 9772 25 18 9773 3 1.4 9774 1.2 nd nd = not determined All 10 animals were also tested for hLZ expression. Only animal 9772 showed expression of hLZ in saliva. The amount detected was 2 ng/ml. Of the 21 animals born in the experiment described in Example 15, one animal (male) was judged to be moεaic based on the tact that it was immunotolerant for hLF. This animal showed an hLF expresεion in saliva of 100 ng/ml . These data show that the transgenes uεed are capable of expressing hLF (and hLZ) in bovines. Having described the preferred embodiments of the present invention, it v/ill appear to those ordinarily skilled in the art that various modifications may be made to the disclosed embodiments, and that εuch modifications are intended to be within the εcope of the present invention. All references disclosed herein are expressly incorporated by reference.

Claims: WHAT IS CLAIMED IS: 1. A transgene for producing a recombinant polypeptide in transgenic bovine species compriεing at leaεt one expression regulation DNA sequence functional in at leaεt one cell-type of said bovine species operably linked to a recombinant DNA encoding a recombinant polypeptide, wherein said tranεgene iε capable of directing the expreεεion of εaid recombinant DNA sequence in at least εaid one cell-type of a bovine εpecieε containing εaid transgene to produce said recombinant polypeptide. 2. The transgene of Claim 1 wherein said expression regulation sequences comprise 5 ' and 3 ' expression regulation sequenceε from a εerum albumin, εaid cell- type iε liver cell, said recombinant polypeptide is human serum albumin and said transgene further comprises a secretory DNA sequence functional in εaid liver cells and operably linked to the recombinant DNA encoding said human εerum albumin. 3. A transgene for producing a recombinant polypeptide in the milk of transgenic bovine εpecieε compriεing at leaεt one expreεεion regulation DNA εequence functional in the mammary εecretory cellε of εaid bovine εpecies, a secretory DNA sequence encoding a εecretory εignal sequence also functional in the mammary εecretory cells of εaid bovine species and a recombinant DNA sequence encoding a recombinant polypeptide, wherein said secretory DNA sequence is operably linked to said recombinant DNA sequence and to form a secretory- recombinant DNA sequence εaid at leaεt one expreεsion regulation sequence operably linked to said secretory- recombinant DNA sequence, such that said transgene is capable of directing the expresεion of εaid εecretory- recombinant DNA sequence in mammary secretory cells of bovine species containing said transgene to produce a form of recombinant polypeptide which when εecreted from said mammary secretory cells produces recombinant polypeptide in the milk of said bovine εpecieε. 4. The transgene of Claim 1 or 3 further comprising a recombinant intervening sequence. 5. The transgene of Claim 4 wherein said recombinant intervening sequence is a hybrid intervening sequence. 6. The transgene of Claim 5 wherein said hybrid intervening εequence containε a permiεεive RNA splice signal. 7. The transgene of Claim 3 wherein said recombinant polypeptide is a homologous polypeptide from bovine species. 8. The transgene of Claim 7 wherein said homologous polypeptide is selected from the group consisting of caseins, lactoferrin, lysozyme, cholesterol hydrolase and serum albumin. 9. The transgene of Claim 3 wherein said recombinant polypeptide is a heterologous polypeptide. 10. The transgene of Claim 9 wherein said heterologous polypeptide is selected from the group consisting of human milk proteins, human εerum proteinε, and industrial enzymes. 11. The transgene of Claim 10 wherein said heterologous polypeptide iε a human milk protein. 12. The transgene of Claim 11 wherein said human milk protein iε εelected from the group consisting of εecretory immunoglobulins, lysozyme, lactoferrin, lactoglobulin, α-lactalbumin and bile salt-stimulated lipase. 13. The transgene of Claim 12 wherein said milk protein iε lactoferrin or lyεozyme. 14. The transgene of Claim 10 wherein εaid heterologous polypeptide is a human serum protein. 15. The tranεgene of Claim 14 wherein εaid human serum protein is selected from the group consisting of albumin, immunoglobulin, Factor VIII, Factor IX and Protein C. 16. The tranεgene of Claim 15 wherein εaid serum protein is albumin. 17. The transgene of Claim 10 wherein said heterologous polypeptide is an induεtrial enzyme εelected from the group conεiεting of proteases, lipases, chitenases and ligninaseε. 18. The tranεgene of Claim 3 wherein said secretory DNA εequence iε selected from the group consisting of DNA sequences encoding secretory εignal sequences from human lactoferrin, human serum albumin, human lysozyme and secretory signal sequences from bovine αSl-casein, αS2- casein, 3-casein, κ-casein, α-lactalbumin, β- lactoqlobulin, and εerum albumin. 19. The tranεgene of Claim 18 wherein εaid secretory DNA sequence iε the DNA εequence encoding the εignal εecretion sequence of bovine αSl casein. 20. The tranεgene of Claim 3 wherein εaid at least one expresεion regulation εequence compriεeε 5' expreεsion regulation DNA εequences operably linked to the 5' end of said εecretory-recombinant DNA εequence. 21. The tranεgene of Claim 20 wherein said 5' expression regulation DNA sequence iε εelected from the group consisting of 5' expression regulation sequence from bovine geneε encoding αSl-casein, αS2-casein, /---caεein, κ-casein, α-lactalbumin, and -lactoglobulin. 22. The transgene of Claim 21 wherein said 5' expresεion regulation DNA εequence iε a proximal 5' expreεεion regulation εequence compriεing the promoter of bovine αSl-caεein. 23. The tranεgene of Claim 22 wherein εaid 5' expression regulation DNA sequence further compriεes a distal 5' expression regulation sequence comprising 5 '-flanking DNA εequence from bovine αSl-casein. 24. The transgene of Claim 20 further comprising 3' expression regulation sequences operably linked to the 3' end of said εecretory-recombinant DNA εequence. 25. The tranεgene of Claim 24 wherein εaid 3' expreεεion regulation εequence compriεe 3 ' expreεεion regulation εequence from bovine geneε encoding αSl- casein, αS2-casein, 3-casein, k-casein, α-lactalbumin, and jS-lactoglobulin. 26. The tranεgene of Claim 25 wherein εaid 3' expression regulation DNA sequence comprises a 3 ' proximal expresεion regulation εequence from bovine αSl-casein. 27. The tranεgene of Claim 26 wherein εaid 3' expression regulation DNA sequence further compriεes a 3 ' diεtal expression regulation sequence from bovine αSl-casein. 28. The transgene of Claim 27 wherein said distal 5' expression regulation DNA sequence compriseε about a 30 kb 5 '-flanking region of bovine αSl-casein and said diεtal 3 ' expreεεion regulation DNA εequence comprises about a 15 kb 3 '-flanking region of bovine αSl-casein. 29. A tranεgenic bovine εpecieε capable of producing a recombinant polypeptide in at least one cell type of said animal. 30. A transgenic bovine εpecieε capable of producing recombinant polypeptide in the milk of εaid trangenic εpecieε. 31. The transgenic bovine specieε of Claim 30 wherein said recombinant polypeptide is a homologous polypeptide from bovine species. 32. The transgenic bovine species of Claim 30 wherein said recombinant polypeptide is a heterologous polypeptide. 33. The transgenic bovine εpecieε of Claim 32 wherein εaid heterologouε polypeptide iε εelected from the group consisting of human milk proteins, human serum proteins, and industrial enzymes.. 34. The transgenic bovine specieε of Claim 33 wherein said heterologous polypeptide is a human milk protein. 35. The transgenic bovine species of Claim 34 wherein said human milk protein is selected from the group conεiεting of secretory immunoglobulins, lysozyme, lactoferrin, lactoglobulin, α-lactalbumin and bile salt- stimulated lipase. 36. The tranεgenic bovine εpecies of Claim 35 wherein said milk protein is lactoferrinor lysozyme. 37. The transgenic bovine specieε of Claim 33 wherein said heterologous polypeptide is a human serum protein. 38. The tranεgenic bovine specieε of Claim 37 wherein εaid human εerum protein iε εelected from the group consisting of albumin, immunoglobulin, Factor VIII, Factor IX and Protein C 39. The transgenic bovine species of Claim 38 wherein said serum protein is albumin. 40. The tranεgenic bovine εpecies of Claim 33 wherein said heterologous polypeptide is an industrial enzyme selected from the group consisting of proteases, lipases, chitinases and ligninaεes. 41. Milk from transgenic bovine species containing a recombinant polypeptide. 42. The milk of Claim 41 wherein said recombinant polypeptide is a homologous polypeptide from bovine species. 43. The milk of Claim 41 wherein said recombinant polypeptide iε a heterologouε polypeptide. 44. The milk of Claim 43 wherein εaid heterologous polypeptide is selected from the group consisting of human milk proteins, human serum proteinε, and industrial enzymes. 45. The milk of Claim 44 wherein said heterologous polypeptide iε a human milk protein. 46. The milk of Claim 45 wherein εaid human milk protein iε selected from the group consiεting of εecretory immunoglobulinε, lyεozyme, lactoferrin, lactoglobulin, α-lactalbumin and bile εalt-εtimulated lipase. 47. The milk of Claim 46 wherein said milk protein is lactoferrin or lysozyme. 48. The milk of Claim 43 wherein said heterologous polypeptide is a human εerum protein. 49. The milk of Claim 48 wherein εaid human εerum protein is selected from the group consisting of albumin, immunoglobulin, Factor VIII, Factor IX and Protein C. 50. The milk of Claim 49 wherein said serum protein is albumin. 51. A food formulation comprising transgenic milk containing a recombinant polypeptide. 52. The food formulation of Claim 51 wherein said recombinant polypeptide iε at leaεt partially purified from εaid transgenic milk. 53. The food formulation of Claim 51 formulated with nutrients appropriate for infant formula. 54. A method for producing a tranεgenic bovine εpecies capable of producing a recombinant polypeptide in the milk of said bovine species, said method comprising: introducing the tranεgene of Claim 1 into an embryonal target cell of a bovine εpecies; transplanting the transgenic embryonal target cell formed thereby or the embryo obtained herefro into a recipient female bovine parent; and identifying at least one female offspring which is capable of producing said recombinant polypeptide in the milk of said offspring. 55. A method for producing a transgenic non-human mammal having a desirable phenotype comprising: (a) methylating a transgene capable of conferring said phenotype when incorporated into the cellε of said transgenic non-human animal; (b) introducing εaid methylated transgene into fertilized oocytes of said non-human mammal to permit integration of said transgene into the genomic DNA of said fertilized oocytes; (c) culturing the individual oocytes formed hereby to pre-implantation embryos thereby replicating the genome of each of said fertilized oocytes; (d) removing at least one cell from each of εaid pre-implantation embryoε and lyεing εaid at leaεt one cell to release the DNA contained therein; (e) contacting said releaεed DNA with a restriction endonuclease capable of cleaving said methylated transgene but incapable of cleaving the unmethylated form of εaid tranεgene formed after integration into and replication of εaid genomic DNA; and (f) detecting which of said cells from said pre- implantation embryos contain a transgene which is resistant to cleavage by said restriction endonuclease as an indication of which pre-implantation embryos have integrated said transgene. 56. The method of Claim 55 wherein εaid removal of at leaεt one cell formε a firεt and εecond hemi-embryo for each of said pre-implementation embryos and each of said first hemi-embryoε iε lyεed and analyzed according to εtepε (d) through (f) , εaid method further comprising; (g) cloning at leaεt one of εaid εecond hemi- embryoε; and (h) to form a multiplicity of tranεgenic embryoε. 57. The method of Claim 56 further comprising transplanting more than one of said transgenic embryos into recipient female parentε to produce a population containing at least two transgenic non-human animals having the same genotype. 58. The method of Claim 55 further comprising transplanting the remainder of said pre-implantation embryo containing a genomically integrated tranεgene into a recipient female parent and identifying at least one offεpring having εaid phenotype. 59. The method of Claim 55 wherein εaid reεtriction endonuclease iε DPNI and εaid tranεgene iε methylated at N6 of the adenine of the εequence GATC contained within said transgene. 60. The method of Claim 59 wherein said detection utilizes a polymerase chain reaction using extension primerε complementary to εequenceε upstream and downstream to said GATC sequence. 61. The method of Claim 59 wherein said non-human transgenic mammal is bovine εpecieε, εaid transgene encodes a recombinant polypeptide and said desired phenotype is the ability to produce said recombinant polypeptide in the milk of εaid bovine εpecies. 62. The method of Claim 61 wherein said transgene is the transgene of Claim 3. 63. A transgene for producing a recombinant polypeptide in the milk of tranεgenic bovine εpecieε comprising: (i) a bovine 5' expression regulation sequence; (ii) a εecretory DNA εequence encoding a secretory εignal sequence functional in the mammary secretory cells of the bovine species; (iii) a recombinant DNA sequence encoding a recombinant polypeptide, said secretory DNA sequence being operably linked to said recombinant DNA εequence, wherein a εecretory-recombinant DNA εequence iε formed, said secretory-recombinant DNA sequence being operably linked to said bovine expression regulation sequence; (iv) a 3' untranslated sequence; (v) a 3 ' flanking sequence of a bovine gene; and wherein said tranεgene iε capable of directing the expreεεion of εaid εecretory-recombinant DNA sequence in mammary εecretory cellε of bovine species containing said tranεgene to produce a form of recombinant polypeptide which when secreted from said mammary secretory cells produces recombinant polypeptide in the milk of said bovine species. 64. The transgene of claim 63, further comprising a recombinant intervening sequence. 65. The transgene of claim 64 wherein the recombinant intervening sequence is a hybrid intervening sequence. 66. The transgene of claim 65 wherein the hybrid intervening sequence comprises a 5' portion of an intervening sequence from bovine α-S j^ -caεein and a 3 ' εequence portion of an IgG heavy chain intervening εequence. 67. The tranεgene of claim 66 wherein the 3' εequence portion is a 3 ' splice signal sequence associated with the J-C segment rearrangement of an IgG heavy chain. 68. The tranεgene of claim 63, wherein the bovine expression regulation sequence and the 3 ' flanking sequence are derived from the same bovine gene. 69. The tranεgene of claim 63, wherein the bovine expression regulation sequence, the 3' untranslated sequence, and the 3' flanking sequence are derived from the same bovine gene. 70. The tranεgene of claim 68 or claim 69 wherein the bovine gene iε α-S- j^ -casein. 71. The transgene of Claim 70 wherein the bovine expreεεion regulation εequence compriεeε about a 30kb 5' -flanking region of bovine αSl-caεein and the 3'- flanking εequence comprises about a 15kb 3 '-flanking region of bovine αSl-casein. 72. The tranεgene of claim 3 or claim 63 wherein the milk comprises greater than 50 micrograms of the recombinant polypeptide per milliliter. 73. A tranεgenic bovine species capable of producing a recombinant polypeptide in saliva. 74. The semen of a tranεgenic bovine. 75. A tranεgene for producing a recombinant polypeptide in the milk of tranεgenic bovine species comprising: (i) a 5' expreεεion regulation sequence; (ii) a εecretory DNA sequence encoding a secretory signal sequence functional in the mammary secretory cells of the bovine species; (iii) a recombinant DNA sequence encoding a recombinant polypeptide, said secretory DNA sequence being operably linked to εaid recombinant DNA εequence, wherein a secretory-recombinant DNA sequence is formed, said secretory-recombinant DNA sequence being operably linked to the 5' expression regulation sequence; (iv) a 3' untranεlated εequence; and, (v) a 3' flanking sequence from a human gene; wherein the transgene is capable of directing the expression of the secretory-recombinant DNA εequence in mammary εecretory cellε of bovine εpecieε containing the transgene to produce a form of recombinant polypeptide which when secreted from the mammary secretory cellε produces recombinant polypeptide in the milk of the bovine species. 76. The transgene of claim 75, wherein the 5' expresεion regulatory sequence is a bovine sequence. 77. The tranεgene of claim 75 or claim 76, wherein the 3' flanking εequence is from the human lactoferrin (hLF) gene. 78. The transgene of claim 77, wherein the 3' flanking sequence is 9 kilobaεe pairε in length. 79. The transgene of claim 77, wherein the recombinant polypeptide is human lactoferrin. 80. The transgene of claim 75, wherein the 5' expression regulation sequence, the secretory DNA sequence, the recombinant DNA sequence encoding a recombinant polypeptide, the 3' untranslated sequence; and the 3' flanking εequence are from a human gene. 81. The tranεgene of claim 80, wherein the human gene iε the lactoferrin gene. 82. A method for expreεεing a human polypeptide in the milk of a bovine compriεing: introducing a human genomic fragment encoding the human polypeptide into an embryonal target cell of a bovine εpecieε; tranεplanting the tranεgenic embryonal target cell formed thereby or the embryo obtained therefrom into a recipient female bovine parent; and identifying at least one female offspring which is capable of producing the recombinant polypeptide in the milk of the offεpring. 83. The method of claim 82, wherein the human polypeptide is lactoferrin.

Inventors: DEBOER HERMAN A, HEYNEKER HERBERT L, LEE SANG HE, PIEPER FRANK, PLATENBURG GERARD, STRIJKER REIN, DEBOER, HERMAN, A., HEYNEKER, HERBERT, L., LEE, SANG, HE, PIEPER, FRANK, PLATENBURG, GERARD, STRIJKER, REIN
Applicants: DEBOER HERMAN A, GENPHARM INT, HEYNEKER HERBERT L, LEE SANG HE, PIEPER FRANK, PLATENBURG GERARD, STRIJKER REIN, GENPHARM INTERNATIONAL, INC.
Application year: 1993
Main classification: C07H21
IPC codes: A01K67, A23C9, A61K48, A61P15, C07H21, C07K14, C12N9, C12N15, C12P21