256
ABSTRACTS
organs of the male. For semen collected from the vagina direct, the possibility of con
tamination by bacteria in the vaginal secretion should be excluded by previous examina-
tion of the vagina and the adoption of necessary precautions. The hydrogen ion concentra-
tion is determined by the use of an electric potentimeter with calomel cell and quin¬
hydrone. A more recent and critical method of evaluating the quality of sperm has
been evolved by gauging the respiration of spermatozoa. The correlation of sperm
respiration with breeding performance provides a reliable index of fertility.
The methods of insemination in different species of females are essentially the
same.
and the cervix is exposed and the required quantity of diluted semen is introduced, either
in gelatine capsules or by means of an inseminator. The best results with artificial
insemination are obtained by introducing semen well into the cervix, or with some species
direct into the uterus. Vaginal inseminations do not record a high percentage of success.
Inseminations should either coincide with ovulation or precede it by a few hours as
the life of spermatozoa in the reproductive tract of the female is relatively short. As
ovulation generally occurs late in the oestrum, the insemination should be timed to
coincide closely with it. In practice the latter half of the oestrum has been found to be
the best time for insemination. Two or more inseminations are indicated in a female
with a long period of oestrum. In mares over 80.5 per cent of pregnancies were obtained
by mating them 4 to 48 hours before ovulation as determined by palpation of maturing
follicle. Mares begin to go out of heat from 6 to 18 hours after ovulation and they refuse
to accept the stallion after 24 to 48 hours. Investigations, however, show that repeated
service during the latter half of the oestrum in all species of animals ensures a larger
number of successful impregnations.
The quantity of semen to be used in artificial insemination depends on many factors,
e.g. the quality of semen, the number of viable sperms, the stage of oestrus, the state of
the reproductory organs of the female and the region where the semen is introduced. The
quantities of semen found adequate for impregnating females of different species of
domestic animals are given as :—
Mare . . . .
Cow . . . .
Sheep . . . .
Sow . . . .
Chicken . . .
10 to 25 c.c.
.05 to 2 c.c.
.01 to 0.2 c.c.
50 to 100 c.c.
.1 c.c.
Males used either for artificial insemination or natural breeding must be kept in the
best possible condition of health. This is done by allowing properly balanced food with
abundant supply of green fodder and regular exercise. Under proper management and
training, a good deal of difficulty in obtaining a quick and efficient service is eliminated
and the male can be easily trained to mount a dummy or a female out of heat.
The influence of frequency of service on relative productive capacity and the quality
of ejaculate varies in different species of animals or even individuals. For those species
that produce a large volume of ejaculate at each mating, e.g. the horse, the dog and the
boar, the sperm number for each ejaculate and viability decrease rapidly, while in the
bull and the ram a great many matings can be made in a relatively short interval without
deletrious effect. A rest period of 24 hours is sufficient to restore the sperms to normal.
In boars, however, an interval of 2 days' rest after one mating a day is indicated.
In bulls and rams many successive matings in one day can be made without depleting the
sperm supply, but two services a day is held as the optimum. There is also a seasonal
variability in sperm production in different species and this is more apparent in dogs in
the breeding season.
To obtain the largest percentage of conception the preservation of the semen by spe-
cial treatment in a state of viability, if not used immediately after collection, is necessary.
Temperature shock, air, water or harmful chemical agents and direct exposure to sunlight
should be scrupulously avoided.
If inseminations are to be done within two hours after collection, the semen can
simply be preserved in a clean and dry stoppered vial, kept in room temperature in a dark
place. For preservation for a longer period, the following technique is followed. Im-
mediately after collection the semen is placed in a clean vial and covered with a layer