In vitro culture method for a fertilized ovum of a hen

Abstract: A fertilized ovum (1) is placed in a container (2) containing a thin albumen (3). A yolk (1b) of the ovum (1) is covered with a sheet of gauze (4), and the ovum (1) is cultured up to the blastoderm stage (stage X).

Description: BACKGROUND OF THE INVENTION The present invention relates to an in vitro culture method for culturing a fertilized ovum of a hen. There is known a culture method where an ovum of a hen which has just been fertilized is submerged in albumen at a temperature of 41°C for the culture thereof. The ovum can be developed up to an early stage of cell division, but not up to the blastoderm stage (stage X). In order to culture an undivided fertilized ovum of a hen, the ovum is placed in a glass container filled with a culture medium which is a mixture of thin albumen and salt solution mixed in the ratio of 3:2. The glass container is sealed with a sheet of transparent plastic film. The ovum is thereafter cultured at a temperature between 41°C and 42°C. The undivided ovum can thus be developed up to the end of the blastoderm stage (stage X). However, in this case it is necessary to take out the fertilized ovum with sufficiently thickly formed albumen from a lower portion of the magnum of oviduct, 165 minutes after the oviposition, or 135 minutes after the ovulation. In this respect, The Journal of Experimental Zoology 254, 1990, 322 - 326 discloses a method wherein fertilized ova surrounded by a partially formed capsule of thick albumen were obtained from the magnum of the oviduct at a distance of 0 - 15 cm from the junction between the magnum and isthmus (2.5 - 2.75 hr after oviposition of the preceeding egg). The ova were placed in glass jars with culture medium (three parts thin albumen, one part salt solution), the jars sealed with plastic film and the preparations incubated at 41.5°C for 24 - 24.5 hr. The ovum which has just been fertilized is positioned in an upper portion of the magnum of oviduct. At that stage, only mucin albumen and a thick particulate albumen are formed around the yolk, so that the fertilized ovum cannot be successfully developed up to the blastoderm stage (stage X) by the culture method mentioned above. SUMMARY OF THE INVENTION The object of the present invention is to provide a method of culturing an ovum of a hen wherein a freshly fertilized ovum is developed in vitro up to the blastoderm stage (stage X) so that the embryonic development may be advanced to the hatching stage by combining the recently devised culture method using surrogate eggshells. According to the present invention there is provided an in vitro culture method for a fertilized ovum of a hen comprising placing the fertilized ovum in a container containing a thin albumen, covering a yolk of the ovum with a sheet of gauze, and culturing the ovum up to the blastoderm stage (stage X). In one aspect of the invention, the ovum in the container is positioned such that a germinal disk is located at a top of the yolk. The fertilized ovum is taken out from an upper portion of the magnum of oviduct of a hen. Further objects and features of this invention will be understood from the following description with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a sectional elevational view showing an ovum in a container to which the in vitro method according to the present invention is applied; and Fig. 2 is a plan view of the container of Fig. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, an ovum (embryo) 1 which has just been fertilized is taken out from an upper portion of the magnum of oviduct of a hen, 60 to 80 minutes after the oviposition, or 30 to 40 minutes after the ovulation. As shown in Figs. 1 and 2, the ovum 1 is placed in a glass container 2 having an inner diameter of 45 mm and a height of 50 mm, and 5 ml of thin albumen 3 is poured into the container 2. A yolk 1b of the ovum 1 is rotated so that the germinal disk 1a is positioned at the top of the yolk 1b. A sheet of gauze 4 of three centimeters square is so disposed as to cover the yolk 1b including the germinal disk 1a. The four corners of the gauze 4 are soaked in the surrounding thin albumen 3. The opening of the glass container 2 is covered with a sheet of plastic film 5 which is held in position by a rubber band 6 to seal the opening of the container 2. The ovum 1 is cultured in this condition for 26 hours at a temperature of between 41°C and 42°C, preferably 41,5°C. The ovum 1 is cultured by the method of the present invention up to the blastoderm stage (stage X). The ovum 1 is thereafter cultured by the recently devised method using surrogate eggshells for hatching. The following table shows the viability and the hatching rate of the fertilized ovum by the method of the present invention up to the blastoderm stage (stage X), and further by the known methods after blastoderm stage. The table further indicates, for comparison, the results obtained with laid eggs cultured by the recently devised culture method. Viability and Hatching Rate of Ovum of Hen Number of Days After Ovulation Present Invention Laid Egg 0 n=82 1 : n=44 2 : : 3 : : 4 46.3 100.0 5 32.9 100.0 6 32.9 97.7 7 31.7 97.7 8 30.5 93.2 9 30.5 93.2 10 30.5 93.2 11 30.5 93.2 12 30.5 93.2 13 30.5 93.2 14 30.5 93.2 15 30.5 93.2 16 30.5 93.2 17 30.5 93.2 18 30.5 90.9 19 30.5 86.4 20 30.5 84.1 21 30.5 79.5 22 24.4 68.2 Hatch 19.5 43.2 As shown in the table, at least 46,3 % of the fertilized ova cultured by the method of the present invention have developed to the blastoderm stage (stage X), and 19,5 % have hatched. From the foregoing it will be understood that the present invention provides a method of culturing a fertilized ovum wherein the ovum is developed to the blastoderm stage (stage X) by the in vitro culture starting immediately after the fertilization.

Claims: An in vitro culture method for a fertilized ovum of a hen comprising the steps of: a) recovering the fertilized ovum (1) from an upper portion of a magnum of an oviduct of a hen 60 to 80 minutes after oviposition; b) placing the fertilized ovum (1) in a container (2) containing thin albumen (3) and partially submerging the fertilized ovum in said thin albumen (3); c) covering a yolk (1b) of the ovum (1) with a sheet of gauze (4), said gauze (4) contacting said yolk (4) and said thin albumen (3); and d) culturing the ovum (1) so covered with said gauze (4) up to the blastoderm stage. The method according to Claim 1, wherein the ovum (1) in the container (2) is positioned such that a germinal disk (la) is located at a top of the yolk (1b). The method according to Claim 1 or 2, wherein an opening of the container (2) is covered with a sheet of plastic film (5) which is held in position by a rubber band. The method according to any of Claims 1 to 3, wherein the ovum (1) is cultured for 26 hours at a temperature between 41°C and 42°C.

Inventors: NAITO MITSURU, NIRASAWA KEIJIRO, OISHI TAKAO, NAITO, MITSURU, NIRASAWA, KEIJIRO, OISHI, TAKAO
Applicants: DIRECTOR GENERAL NATIONAL INST, DIRECTOR-GENERAL, NATIONAL INSTITUTE OF ANIMAL INDUSTRY
Application year: 1991
Main classification: C12M3
IPC codes: A61D19, C12M3, A01K67