174 APPLICATION OF ARTIFICIAL INSEMINATION IN CATTLE [Vol. XXII, Part III,
for nine bulls, and for the Cambridge centre as 1.31 to 1.86 for five bulls by Towson
[1944]. The average estimated fertility for all centres in England is given as 66.2
per cent by the figures published by the British Ministry of Agriculture [1946].
In Italy, Vighenzi [1946] states that in five years 5,796 inseminations were needed
to fertilise 3,747 cows which give an average service rate of 1.6. The average
service rates so far observed at the three Government of India centres are decidedly
better than the American, British and Italian figures.
In Table VI is given a comparative study of the relative influence of volume,
age and treatment of semen on fertility. The available data have been divided
into two main groups according to species. Each in turn is further divided into
two sub-groups, according to the volume of semen injected. Each sub-group in
turn is arranged vertically into four main classes according to the age of the semen
used. Figures for neat and diluted semen are presented separately.
From Table VI (on page 175), it will be seen that slightly higher fertility is
obtained when 1.0 c.c. of semen is used instead of 0.5 c.c. This is true irrespective
of treatment (neat or dilute) of semen. This is in keeping with the findings of
Walton [1933] who observed a decrease in percentage of conception with a decrease
to 0.5 c.c. or an increase to 5 c.c. above the optimum 1 c.c. and contrary to the
observations reported by Kozlova [1935] and Herman [1939]. The former found no
significant difference in the calving percentage of cows inseminated by the cervi-
cal method with 0.2, 0.5, 1.0, and 2.0 c.c. of semen, while the latter reported very
little difference in the conception rates when quantities varying from 0.1 to 6.0
c.c. were used for artificial insemination.
Comparing on like basis, it is observed that, with a single exception (which
may as well be due to the fewer number of inseminations included), the diluted
semen gave better results than neat semen. Further, there was no apparent decrease
in fertility with age of semen up to- 76 hours at Montgomery and Patna centres.
At Calcutta Centre, however, there is an indication of lowered fertility with the use
of aged semen. The latter results confirm the findings of Milovanov and Kulesova
[1945], who found a reduction of 15 to 20 per cent in the number of pregnancies
after 48 to 96 hours of storage at 5° to 8°C, and Underbjerg, Davis and Spangler
[1942] who, using both diluted and neat semen, found a marked increase in service
rates with semen stored for more than 24 hours. As opposed to this, and in line
with the findings at Montgomery and Patna Centres, Willett, Fuller and Salisbury
[1940] observed no important deviation upto 96 hours, with semen stored in yolk-
phosphate diluent. Their data covered 1,500 inseminations and as in our studies,
only sperm not less than +++ motility rating were used. Salisbury [1941, 1943,
and 1944] reported a high percentage of conception with semen stored in yolk-
citrate and yolk-phosphate diluents for as long as 5 days ; further, using different
rates of dilution no detectable effect on fertility level with dilution rate as high as
1 : 100 (without the addition of sulpha drugs) was observed by Salisbury [1946];
Salisbury et al. [1943; 1945]. With the addition of sulpha drugs, the dilution
rate could be further increased [Salisbury and Bratton ; 1948]. In view of the fact
that our data are incomplete in many respects, and the number of inseminations
performed using stored semen is comparatively small, no conclusions are drawn
at present on the influence of age of stored semen on fertility.