In pigs, estrus synchronization may be easily achieved by synchronized weaning of lactating sows; estrus is seen 4–10 days later. Administration IM of a commercially available combination of eCG (400 IU) and hCG (200 IU), per 5 mL dose, given as a single injection within 12 hr after weaning, tightens the synchronization, and estrus is seen 4–5 days after weaning. This eCG and hCG combination also induces estrus in gilts with delayed puberty and in sows with postweaning anestrus. Exogenous PG induces luteolysis of the porcine corpus luteum only after day 12 of the estrous cycle and, therefore, is not a practical agent for estrous cycle control; however, estrus may be synchronized by induction of abortion in sows pregnant >15 days by administration of PGF_2α (15 mg, IM, then 10 mg, IM, 12 hr later) or cloprostenol (1 mg, followed 24 hr later by 0.5 mg); sows return to estrus 4–10 days after treatment. Estrus may also be synchronized by feeding altrenogest (15–20 mg, PO, sid for 14–18 days) or by using bovine norgestomet implants (one implant followed by addition of a second implant 9 days later) removed 19 days after initiation of treatment; neither treatment is currently approved in the USA for swine. Combination eCG and hCG may be given on the day of progestagen withdrawal to better synchronize estrus.

Last full review/revision July 2011 by Steven P. Brinsko, DVM, MS, PhD, DACT