June, 1952]
D. P. MUKERJEE AND P. BHATTACHARYA
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in rams, judged by pH, sperm concentration and the total number of spermatozoa,
deteriorated in autumn and improved in spring.
DISCUSSION
Reaction-time. The study of 'reaction-time' was undertaken with a view to
determine if there was any correlation between sex vigour of the animal and its
fertility. Result obtained in this experiment showed that sex vigour and sperm
production were quite independent of each other. From the records of individual
rams it has been found that rams with high sex vigour were not necessarily good
semen producers. Further, it has been found that seasons did not greatly influence
the sexual behaviour of rams as they did the sperm production. These results
agree with those of McKenzie and Berliner [1937] with ranis, Anderson [1939] and
Mukherjee and Bhattacharya [1947] with bulls.
Volume. Volume of semen was found to be variable among rams and during
the seasons. Phillips et al, [1943, b] also found significant variation among rams
but they did not find significant variation between seasons. McKenzie and Berliner
[1937] observed that volume of semen in rams decreased during the periods of high
environmental temperature. This observation is in agreement with the results
obtained in the present experiment. Under the same climatic conditions in which
experiment was performed, Mukherjee and Bhattacharya [1947] observed no such
seasonal variation in volume of bull semen. It is apparent, therefore, that the
decrease in semen volume in rams during the periods of high temperature associated
with high humidity and rainfall might be due to the reason that rams are more
susceptible to climatic stress than the bulls.
Motility. Motility rating was determined in this experiment by direct micro-
scopical examination. Obviously this method of estimation not only depends on
motility of spermatozoa but on sperm concentration as well. This might be the
reason why in autumn when the sperm concentration was lower than in spring the
initial motility was also found to be lower. There was no direct proportional increase
in initial motility with the increase in sperm concentration during the different
seasons. Had it been so, in winter and autumn when there was no significant
variation in initial motility there should have been no variation in sperm concentra-
tion as well. But the result indicated that in autumn sperm concentration was
significantly lower than in the rest of the seasons. Again in summer initial motility
was significantly higher than in spring but sperm concentration showed just the
reverse trend. Initial motility rating as has been done in this experiment is the
most emperical method of evaluating semen quality. At best it can indicate a good
sample from a bad sample. Grading of fairly good samples by this method alone
is almost impossible. This might be the reason why, although there was highly
significant variation in sperm concentration among rams and between years, initial
motility failed to show any significant variation either among rams or between years.
Phillips et al. [1943, b] obtained significant variation between rams within breed
as well as between seasons which is in disagreement with the result of the present
investigation. Our result is, however, in agreement with what has been reported
by Phillips and his co-workers [1943, a] in bulls.
Hyderogenion concentration. From the records of individual animals it has
been found that semen samples with higher pH. value were usually poorer