Use of PMSG in the prevention of seasonal post-weaning anestrus in sows.

PMSG (500 I.U.; administered I.M.) prevented post-weaning anestrus when given to sows weaned during the months of August, September and October compared to untreated controls during the same months. During winter and spring months, there was no difference in the post-weaning return to estrous rate for treated and control sows. Control sows had a greater degree of estrous synchrony following weaning during winter and spring months compared to summer months. PMSG-treated sows were in estrus earlier (frequently Day 3) than controls. Results indicate that PMSG, given at weaning, is effective in preventing summer-early fall post-weaning anestrus.