The male effect associated with prostaglandins and reproductive outcomes in photo-stimulated Saanen goats during the non-breeding season

Abstract

The efficiency of combining oestrous induction via a light program (16 h of light and 8 h of darkness for 60 days, ending on Day 0 - D0) with cloprostenol administration, followed by the male effect or not, was tested in acyclic Saanen goats during the non-breeding season (June/2019 to January/2020). Initially, all animals (males and females) were submitted to the described light program; 60 days after its ending (D60), the females were divided into two groups, with (G1; n = 67) or without (G2; n = 61) a male effect from D60 to D75 after the light program. At D75, both groups received two cloprostenol doses (120 μg; intramuscular) 7.5 days apart (D75 and D82.5). Artificial insemination was performed at a specific time according to the oestrous onset (approximately 68.4 ± 1.2 h between the second cloprostenol dose and IA). Ultrasound scans were performed at different intervals to evaluate follicular dynamics and confirm pregnancy. At the first cloprostenol dose (D75), the proportion of does with at least a corpus luteum (CL), which indicates resumed cyclicity, was greater in G1 than in G2 (85.2% vs. 48.8%; p < .05), although no difference was found at the second dose (p > .05). The adjusted pregnancy rates (number of pregnant goats/oestrous goats) differed between G1 and G2 (21.7% vs. 42.0%; p < .05). G1 also showed a higher frequency of functional CL (based on blood flow and morphology) compared to G2 (96.9% vs. 66.7%; p < .05) at D116. A male effect using photo-stimulated bucks after the first cloprostenol dose increased the number of does presenting CL after buck removal, and no impairment in the pregnancy rates of multiparous does was found.

Keywords: artificial insemination; light program; oestrous synchronization and induction.