Days 4 and 5. The results of this trial are given in Table I.

(b) Numbers of spermatozoa per insemination.

These trials were carried out on a split ejaculate basis and in
the first 500 x 10 spermatozoa per insemination was compared
with 2,000 x 106, the diluted semen being used on the day of
collection and the two succeeding days. The results are given
in Table II.

Since the farrowing rates from the use of 500 x 106
spermatozoa were disappointing, it was decided to compare
2,000 x 100 with 1,000 x 10° spermatozoa per insemination. Two
fertility trials have been completed, Trial A, in which the semen
was used on the day after collection (Day 2) and the subsequent
day (Day 3) and Trial B, in which semen was used on the day of
collection (Day 1) and on the two subsequent days (Days 2 and 3%
see Table III.

The data in Table III are largely self-explanatory but
they showed that when semen diluted in modified I1lini Variable
Temperature was used up to 5 days after collection there was no
apparent difference in fertility between Day 1 and Day 5, using
2,000 million spermatozoa per insemination. These results
suggest that it would be possible to have semen available
continuously from a specific boar provided that it was collected
every sixth day. Whether similar results could be obtained using
smaller numbers of spermatozoa per insemination is not known.

The average ejaculate from the boar contains approximately
80,000 x 106 spermatozoa and this will be sufficient for only 40
inseminations if 2,000 x 106 are used for each insemination.
Reducing the number of spermatozoa to 1,000 x 10° would present
a considerable advantage and one trial suggested that this could
be done without reducing fertility. The results of a second
trial, however, were at variance with this and further
investigations must be donducted to clarify the matter. 6
Certainly the reduction of the number of spermatozoa to 500 x 10
would not be indicated by the results of these trials as using
this number lowers fertility by 12.1 percentage units.

The overall fertility obtained in these trials was sub-
standard and only in one group where the farrowing rate was
76.5 per cent. were the results entirely satisfactory. It will
also be noticed that there are inconsistences in the results
particularly in relation to the use of 1,000 x 10° spermatozoa

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