The Effect of a Sustained-Release Injection of Human Chorionic Gonadotropin on Corpus Luteum Formation and Progesterone Secretion in Beef Heifers

Abstract

A sustained-release injection of human chorionic gonadotropin (HCG) was administered to Syncro-Mate B® synchronized beef heifers 12 hours afer estrus. The sustained-release formulation doubled the ovulation rate, increased corpora lutea size, increased the incidence of cystic corpora lutea, and tended to increase progesterone concentrations. Sustained release of HCG produced effects similar to larger doses and/or multiple aqueous injections of HCG. The doubling of multiple ovulations may have been a result of availability of persistent follicles caused by the Syncro-Mate B® The increase in corpora lutea size was partially caused by the more frequent presence of fluid-filled cavities within the corpora lutea (cystic corpora lutea). In summary, the sustained-release injection of HCG accomplished similar effects as larger doses and/or multiple administrations of nonsustained-release formulations of HCG.