Effect of two routes of administration of human chorionic gonadotropin upon oestrus induction and reproductive outcomes in adult acyclic mix-breed goats

Abstract

The effectiveness of two routes of administration of human chorionic gonadotropin (hCG) upon oestrus induction in anoestrus mix-breed goats was evaluated. Goats [n = 27, 39.6 ± 2.18 kg live weight and body condition score of 1.71 ± 0.02 units (scale 1–5)] were primed with 20 mg P4-intravulvosubmucosal (IVSM) 24 h prior to hCG administration. Thereafter, goats were randomly allocated to three groups to receive 100 IU hCG (0.1 mL) intramuscular (IM, n = 9), or IVSM (n = 9), and saline (0.5 mL) IM injection (CONT, n = 9). Ovarian follicular or luteal tissue was monitored by transrectal ultrasonographic scanning 15 days pre-and 5 days post-treatment. Besides, goats were daily monitored (0800 and 1800 h) × 15 days to detect oestrus signs with the use of aproned sexually active bucks, treated with testosterone; 12 h after the onset of oestrus, goats were mated. While the CONT-goats never depicted neither oestrus nor ovulation (P < .05), the ovarian response from the IM and IVSM groups was 89% vs 68%, respectively (P > .05). Oestrus response (83.5%), pregnancy (60.6%) and litter size (1.55 ± 0.2) did not differ (P > .05) between the IM and IVSM groups. A single application of 100 IU hCG, irrespective of administration route, induced sexual activity in acyclic goats, generating key out-of-season reproductive outcomes.