Reproductive efficiency of treated Karakul ewes with short-term progesterone and hCG injections during the non-breeding and breeding seasons

Abstract

The aim of this study was to evaluate reproductive efficiency of ewes following a short-term treatment with progesterone (P4) plus human chorionic gonadotropin (hCG) injections. In Exp 1, ewes (n = 65) were used during the non-breeding season and received P4, three times every other day (n = 22, 3PHCG, IM) or a single dose of P4 (n = 21, PHCG). We injected hCG in all ewes 24 h after the P4 treatment, and distilled water in control group (n = 22). Blood collection were performed on days −13, −6 and + 8 relative to ram release. In Exp 2, during the breeding season, ewes (n = 66) were assigned to the 3PHCG (n = 33) and control (n = 33) groups described for Exp 1, and subsequently received PGF2α 48 h before ram release. Pregnancy diagnosis was performed on day 42 after the ram release which was done 24 h after the hCG injection. In Exp 1, Estrus, pregnancy rate at induced estrus, and lambing rates at the first cycle were greater in 3PHCG (81.8%, 59.1% and 54.5%) group compared with the PHCG (38.1%, 23.8% and 19%) and control (0%, 0% and 0%) groups (P < 0.05). In Exp 2, Estrus, pregnancy rate at induced estrus, and lambing rates at the first cycle were greater in 3PHCG (75.8%, 57.6% and 51.5%) group compared with the control (39.4%, 30.3% and 27.3%) groups (P < 0.05). To conclude, hCG injection 24 h after P4 administration is an effective protocol to induce fertile estrus during non-breeding season, and synchronize estrus and lambing of ewe in the breeding season.