Effectiveness of different hCG and GnRH based protocols in progesterone primed goats on estrus induction and reproductive outcomes in out-off-season goats

We evaluated whether Gonadotrophin releasing hormone incorporation to the Human chorionic gonadotropin protocol improves the sexual response during the natural anestrous season in goats. Thirty-two adult multibreed anovulatory goats (n = 8, four groups), received 20 mg progesterone i.m. on d-1; on d0, all goats received 7.5 mg prostaglandin F i.v. and control group (CG) 0.5 mL of saline i.m., hCG group (GH) 100 IU of hCG i.m., hCG+GnRH group (GN) 100 IU hCG i.m. + 8.4 μg of GnRH at once, and hCG+GnRH-24h group (GN24) 100 IU hCG i.m. + 8.4 μg of GnRH 24 h apart. GN, GN24 and GH depicted estrus and ovulatory activity, favoring the GH (25%, 25% and 100% for both variables, respectively). Regarding pregnancy rate, the largest values (P<0.05) were observed in GH (12%, 12% vs 75%, respectively). A protocol based on P₄+PGF+hCG was the best option to induce and synchronize estrus as well as ovulation regarding the administration of GnRH during the natural anestrous season in goats.