Concentrations of luteinizing hormone, oestradiol-17beta and progesterone in the plasma of heifers treated to induce superovulation.

Concentrations of luteinizing hormone (LH), oestradiol-17beta and progesterone were studied in 14 heifers treated with pregnant mare serum gonadotrophin (PMSG) and an analogue of prostaglandin F2alpha (PGF2alpha) 48 h later to induce superovulation. Plasma levels of oestradiol-17beta before ovulation and of progesterone after ovulation were related to the number of ovulations but the concentrations of LH were not so related; however, hormone concentrations at the time of injection of PMSG could not be used to predict the rate of ovulation. The injected gonadotrophin also appeared to affect folliculogenesis after ovulation and this may explain the presence of large follicles in the ovary when the corpora lutea were counted. It was possible to demonstrate by analysis of plasma levels of hormones that few non-superovulated animals were really insensitive to PMSG.