The negative effect of repeated equine chorionic gonadotropin treatment onsubsequent fertility in Alpine goats is due to a humoral immune response involving the major histocompatibility complex

In dairy goats, the use of eCG as a convenient hormone for the induction of ovulation is necessary for out-of-season breeding and artificial inseminat ion. However, repeated eCG treatments are followed by decreased fertility i n goats inseminated at a fixed time after treatment. In this report, we sho w the presence of anti-eCG antibodies in plasma of treated goats. A 500 IU eCG injection induces a humoral response, with variable concentrations of a nti-eCG antibody being produced in individual goats. The analysis of succes sive anti-eCG immune responses over several years has demonstrated the exis tence of different populations of goats, defined as low, medium, and high r esponders. By the use of two caprine microsatellites located inside (OLADRB ) and outside (BM1258) the major histocompatibility complex (MHC), a signif icant association (p < 0.05) between the anti-eCG antibody response and som e MHC-DRB alleles was found. Goats with high antibody concentrations at the time of eCG injection (> 2.5 mu g/ml) exhibited a much lower kidding rate than did other females (41.3% vs. 66.7%). Lower fertility of these goats, i nseminated at a fixed time after eCG treatment, might be due to the observe d delay in estrus occurrence and the preovulatory LH surge.