Synchronization of ovulation and artificial insemination of sows after lactation.

The administration of PMS:HCG proved satisfactory as a method for synchronizing estrus and ovulation in sows after 3 or 6 weeks of lactation and permitted artificial insemination at one time without relying on the detection of estrus. Fifty-eight Duroc sows were assigned randomly as controls or to a hormonal-treatment group when their litters were weaned at 3 or 6 weeks of age. Twenty-nine sows (Group I) received no treatment and were inseminated 24 hr after the onset of estrus. Twenty-nine sows (Group II) received a subcutaneous injection of 1,000 IU of PMS the following morning after the litter was weaned and subsequently were injected intramuscularly with 500 IU of HCG either 72 hr (3-week weaning) or 56 hr (6-week weaning) after the injection of PMS. Group II sows were inseminated 24 hr after the HCG injection. All sows were slaughtered at approximately 30 days of gestation. The onset of estrus was confined to a 2-day period for treated sows and occurred over a 7-day period for control sows. The same pregnancy rate (96%) was observed for PMS:HCG-treated sows inseminated 24 hr after HCG administration, and for control sows inseminated 24 hr after the onset of estrus, indicating that hormonal treatment after weaning successfully synchronized ovulation. Ovulation rate and litter size at 30 days after breeding were significantly (P<.01) increased by PMS: HCG treatment. (