ABSTRACTS
73
similarly inseminated with successful results. First-class
sires, in other words proven sires, whose ability to trans-
mit desirable characters has been determined, are very
few ; for in dairy practice the majority of sires are never
proved owing to their destruction or decay before their
worth has become known. Generally a bull reaches the
age of 5 or 6 years before even the first of his daughters
comes into production, and it takes a few more years
before there is a sufficient number of daughters to indi-
cate his value as a transmitter. With co-operative
artificial breeding, it has become possible to have a suffi-
cient number of daughters to prove a bull earlier than
under natural conditions. Due to the progress made in
the storage and transport of semen, the mating of widely
separated animals has been brought within the realm of
reality.
In the operation of artificial breeding no mating involv-
ing actual contact of animals takes place, and therefore
the danger of dissemination of certain contagious diseases,
viz. trichomoniasis, infectious vaginitis, contagious
abortion and metritis, is entirely avoided. Artificial
insemination under large-scale field conditions used
rationally or in conjunction with expert diagnosis by
veterinary surgeons can play an important role in the
control of certain well-defined reproductory disorders of
livestock.
Apart from the control of venereal diseases ensured by
the strict and regular examination of bulls by veterinary
surgeons, sterility in cows due to anatomical deformity
can be easily overcome by artificial breeding. With cows
which fail to breed after repeated services, it is desirable
to try artificial insemination before recommending their
destruction. During extreme cold weather breeding bulls
have been noticed to suffer from temporary sterility or
low breeding efficiency which is said to be associated
with vitamin C deficiency. This condition is often not
detected until a large number of cows have been covered,
and this causes a considerable disturbance of the breeding
programmes. It is an advantage, therefore, to be able
to collect the semen of these bulls by means of an artificial
vagina and test it, as soon as the condition is suspected.
Some recent work in the U.S.S.R. indicates the possi-
bility of artificial determination of sex by the separation of
male and female-determining sperms by the method of
electrophoresis, i.e. accumulation of male and female-
determining sperms in cathode and anode respectively.
The success of this method will have a striking effect on
the future development of dairying and animal industry.
It was not until 1933 that the first detailed account of
the progress and technique of artificial insemination was
published in Great Britian by Walton, who himself is
now acknowledged to be one of the leading authorities
in this field.
The application of artificial insemination on organized
lines in Great Britain offers great possibilities in live-stock
improvement in that it provides the small farmers, who
are responsible for producing one half of the total milk
yield, with the use of a much better sire than they could
individually own and thus the non-pedigree breeders will
have the opportunity of grading up their stock. Results
observed in the U.S.A. and Denmark appear to indicate
that the suggestion of a possible adverse effect of artificial
insemination on the trade of pedigree sires in Great Britain
is without any foundation, but on the contrary it will
provide an incentive to breeders who are eager to improve
their important stocks for post-war periods. The con-
templated legislation by the Ministry of Agriculture to
safeguard the successful establishment of this practice
by restraining its use to properly authorized persons in all
cases and the need for close scrutiny of breeding bulls to
be used for fertility and quality indicate that the veteri-
nary surgeon, in virtue of his training and experience, is
eminently suited to supervise the work of organized arti-
ficial breeding. In Great Britian there is evidence of
growing interest amongst small breeders and dairy
farmers as to the necessity of organized artificial breeding.
This is borne out by the fact that two schemes for the
formation of artificial breeding centres at Cambridge and
Reading have been approved by the Ministry of Agricul-
ture. Similarly private schemes and those sponsored by
breed societies are being launched in co-operation with
the veterinary profession. [S.K.S.]
The effect of processing on the nitrogen distribu-
tion in milk. S. G. MENEFEE, O. R. OVERMANN
and P. H. TRACY (1941). J. Dairy Sci. 11,
953-68
ROWLAND'S simi-micro procedure for the determina-
tion of total casein, non-casein, non-protein, globulin,
albumin and proteose nitrogen was adopted for some
processed milks which gave the following results with the
mixed herd milk. (1) Homogenization of skim milk, 4 per
cent whole milk and 8 per cent whole milk at normal (2,500
lb.) and abnormal (3,500 and 5,000 lb.) pressures gave
no significant changes in the nitrogen distribution.
(2)
Forewarming of milk at 203°F. before condensing coagu-
lated all the albumin which is co-precipitated with casein
at a pH 4.6, with the casein causing high results for
this fraction. This change is significant in all samples of
condensed milk. (3) In evaporated milk the significant
changes are the coagulation of albumin and most of the
globulin, and an increase in non-casein nitrogen indicating
hydrolysis of casein nitrogen. (4) Conden ed skim milk
gave minor changes in the nitrogen distribution. (5)
Holder pasteurization (145°F. for 30 minutes) of milk
produced no changes in nitrogen distribution (6) Re-
pasteurization of skim milk at 190°F. for 30 minutes
coagulated all the albumin. (7) In cultured milk slight
hydrolysis of casein occurred. Pasteurized skim milk
was re-pasteurized for 30 minutes at 190° F. and cooled
to 70°F. and starter was added at the rate of 1 quart of
starter to 25 gallons of milk. The milk was kept over-
night. This cultured milk (acidity 0.79 per cent) was
analysed on the next day. A decrease in casein nitrogen
occurred which was attributed to slight hydrolysis. The
buffers used (sodium acetate and acetic acid) in the deter-
mination of non-casein nitrogen and proteose peptone (plus
non-protein nitrogen) tend to function efficiently in sepa-
rating the protein fractions in the cultured milk, regard-
less of the high acidity. The non-casein, non-protein
and proteose nitrogen fractions of these products in-
creased in percentage of nitrogen. Skim milk, sterilized
cultured and sealed in tin cans showed results comparable
with cultured milk. (8) Addition of 1 part of trypsin,
Enzylac, and steapsin to 25,000 parts of 4 per cent raw
milk kept at 145°F. for 30 minutes produced denfinite
hydrolysis of milk proteins, especially of the casein
nitrogen. (9) There is no relationship between nitrogen
distribution and curd tension. The raw milk, pasteu-
rized milk, enzyme treated milk, homogenized milk
and evaporated milk gave curd tension 57, 53, 26, 12
and zero grams respectively. Tentative official and
semi-micro methods for determination of casein gave
higher results than the official method which is attri-
buted to the pH of the filtrates. The semi-micro method
of Rowland compares favourably with the official method
for the nitrogen distribution in milk. [C. P. A.]