Fertility in Goats During the Non-Breeding Season Using a Short-Term Progesterone Priming Protocol With Either GnRH or hCG to Induce Ovulation

The purpose of this project was to compare ovulation and pregnancy rates in goats bred during the non-breeding season using a short-term progesterone (P4) priming protocol with either gonadotropin releasing hormone (GnRH) or human chorionic gonadotropin (hCG) to induce ovulation. While GnRH acts on the pituitary to produce luteinizing hormone (LH) that stimulates ovulation, hCG elicits ovulation by binding directly to LH receptors on the ovary. Our hypothesis was that during the non-breeding season using a hormone that acts at the level of the ovary (hCG) would increase ovulations and pregnancy rates compared to a hormone that acts at the level of the hypothalamus/pituitary (GnRH). Fourteen mixed breed Alpine and Saanen dairy goats were assigned to Group 1 (GnRH, n=6), Group 2 (hCG n=6), or controls (n=2). Progesterone was administered using a controlled internal drug releaser (Eazi-Breed CIDR Sheep & Goat; Pharmacia and Upjohn, New York, NY) inserted into the vagina for three days. Follicle stimulating hormone (Follitropin-V; Bioniche, Belleville, Ontario, Canada) was administered once on the second and third days of P4 priming (32 mg IM). Prostaglandin F2α (PGF2α; Lutalyse; Pfizer, New York, NY) was given (5 mg IM) on the day of CIDR removal. Two days after CIDR removal, Group1 received 50 mcg IM of GnRH (Cystorellin; Merial, Duluth, GA), while Group 2 received 500 IU IM of hCG (Chorulon; Intervet, Millsboro, DE). Control animals received only CIDRs and PGF2α as the other groups. […]