Fertility studies with cryopreserved boar sperm in
weaned sows have been reviewed to illustrate the
conditions for use up to 1985 (Johnson 1985) and also
studies since that time (Table 1). Years of research
indicate that fertility could be achieved with boar sperm
frozen in multiple forms and with variable numbers of
sperm, inseminations and when used in sows and gilts.
The fertility results were variable across methods but
based on conventional insemination using four to six
billion total sperm, there appeared little effect of using
more than six billion total sperm and surprisingly, more
than a single insemination. Up to the time of 1985,
pregnancy rates were variable but with an average of
65% and a litter size of 8.5. Since that time, numerous