This study assessed the efficiency of synchronous estrus induction by light program followed by two doses of cloprostenol in acyclic Saanen goats of different parity orders. Primiparous (n=22) and multiparous (n=33) goats were subjected to 16 h of light and 8 h of darkness for 60 d (D0-D60), starting 10 days after the winter solstice. All goats received 120 µg cloprostenol doses on D130 (morning) and D141.5 (afternoon) (11.5 days apart). Estrus behavior, ovarian follicular dynamics, and serum progesterone (P4) analyses were recorded from D0 to D174 at different intervals. Animals in estrus after D141.5 were randomly assigned into two groups: assisted natural mating (NM) or artificial insemination (AI; 10 to 24 h after estrus onset with frozen-thawed semen). From D57 to D120, 89.0% of goats presented large follicles (5-8 mm) and P4 concentrations were subluteal from D0 to D120. More multiparous compared to primiparous goats (54.5%, 18/33 vs. 18.2%, 4/22) exhibited estrus after both injections. More primiparous compared to multiparous goats (54.5 %, 12/22 vs. 12.1%, 4/33) did not exhibit estrus after any injection. A total of 35 goats (64%) were in estrus after the second prostaglandin injection and were subjected to NM or AI. The conception rate was similar among primiparous (70.0%, 7/10) and multiparous (68.0%, 17/25) goats but the pregnancy rate differed, being 31.8% (7/22) and 51.5% (17/33), respectively. No interaction was found between parity order and P4 concentrations in does that became pregnant or not. Thus, the association between light program (60 d, starting at the beginning of winter) and two cloprostenol administrations 11.5 d apart (starting 70 d after the end of the light treatment) resulted in sufficient synchronous estrus response in multiparous acyclic Saanen goats to reach satisfactory fertility levels after both NM and AI.
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