Factors influencing pregnancy rate and loss after laparoscopic artificial insemination with frozen-thawed semen in Lohi sheep under sub-tropical conditions

Abstract

This study evaluates factors influencing pregnancy rates per artificial insemination (P/AI) and pregnancy loss in Lohi ewes undergoing laparoscopic AI with frozen-thawed semen under sub-tropical conditions. Data from three experiments comprising ewes (n = 358) of mixed parity (nulliparous; NP and parous; P), various body condition score (BCS) and assigned to long-term (LTP, 11 days) and short-term (STP, 5 days) oestrus synchronization regimen across high breeding season (HBS) and low breeding season (LBS) were analysed. Laparoscopic insemination was conducted 54 h post-sponge removal. Pregnancy diagnosis and loss were evaluated on days 35 and 90 post-insemination via ultrasonography. Results showed parity significantly influenced P/AI, with nulliparous ewes achieving higher pregnancy ratios than parous ewes (p = .001). BCS significantly influenced P/AI (p < .05), with a quadratic relationship observed between BCS and season (BCS*BCS*Season; p = .07). Progestin treatment did not significantly influence the ratio of pregnant ewes (p = .07). Pregnancy losses were significantly higher during LBS than HBS (p < .05), irrespective of progestin treatment. In conclusion, parity and BCS significantly influenced P/AI, with BCS demonstrating a quadratic association with season. Ewes bred during LBS experienced higher pregnancy losses than HBS, irrespective of progestin treatment.

Keywords: BCS and progestin type; laparoscopic insemination; parity and season; pregnancy rate and pregnancy loss; sheep.