Page 502 - Anatomy and Physiology of Farm Animals, 8th Edition

The Ovary and Estrous Cycles / 487

will accept him only during the actual Length of Estrus. The estrous period
may range from 15 to 96 hours, with an
estrous period. Ovulation occurs near the
VetBooks.ir termination of estrus, and two or three average duration between 40 and 46 hours.
ovulations may occur in the same estrous
The first estrus after weaning is usually
period. longer and may average 65 hours; it
occurs about 7 to 9 days after weaning of
Time of Breeding. The best time for the piglets.
breeding ewes is middle to late estrus.
Many sows exhibit infertile estrus 1 to
3 days following parturition. In nearly all
Sow of these animals, ovulation does not
occur. It has been suggested that this heat
Sexual maturity in the gilt usually occurs may be caused by estrogen from some
about 7 months of age. source other than the ovary. Ovulation

Length of Estrous Cycle. The average occurs during the latter part of estrus,
estrous cycle in swine is about 21 days, about the second day of the cycle. At each
with a range of 18 to 24 days considered period, 10 to 25 ova are shed, with an aver-
normal. age of about 16 for most breeds.