Effect of Social Rank upon Estrus Induction and Some Reproductive Outcomes in Anestrus Goats Treated With Progesterone + eCG

SIMPLE SUMMARY: The potential effect of social rank [R] (high—HSR; medium—MSR; low—LSR) in anestrus goats subjected to an estrus induction protocol (EIP) primed with progesterone (P4) and receiving a differential equine chorionic gonadotropin (eCG) dose [D] (D100 vs D350) upon some reproductive outcomes in crossbred dairy goats under intensive stall-fed conditions was evaluated. Response variables included estrus induction (EI, %), latency to estrus (LAT, h), duration of estrus (DUR, h), ovulation (OVU, %), ovulation rate (OR, n), corpus luteum size (CLS, cm), pregnancy (PREG, %), kidding (KIDD, %), and litter size (LS, n). Most of the response variables were positively affected by social rank, favoring to the HSR goats (i.e., EI %, DUR h, OVU %, OR n, and CLS cm). In addition, increased OR and PREG occurred in the HSR + D350 group, while D350 increased LS, irrespective of R. Interestingly, since no differences regarding LAT, DUR, OVU, CLS, PREG, and KIDD occurred between D350 and D100, the obtained values support the use of a reduced level of exogenous hormones to induce and generate out-of-season reproductive efficiency. ABSTRACT: We evaluated the possible role of the social rank [R] (i.e., low—LSR, middle—MSR, or high—HSR) in anestrus goats exposed to a P4 + eCG [D] (i.e., 100 or 350 IU) estrus induction protocol (EIP). Adult, multiparous (two to three lactations), multiracial, dairy-type goats (Alpine–Saanen–Nubian x Criollo goats (n = 70; 25°51′ North) managed under stall-fed conditions were all ultrasound evaluated to confirm anestrus status while the R was determined 30 d prior to the EIP. The variables of estrus induction (EI, %), estrus latency (LAT, h), estrus duration (DUR, h), ovulation (OVU, %), ovulation rate (OR, n), corpus luteum size (CLS, cm), pregnancy (PREG, %), kidding (KIDD, %), and litter size (LS, n) as affected by R, D, and the R × D interaction, were evaluated. While OVU and CLS favored (p < 0.05) HSR (96% and + 1.04 ± 0.07 cm), an increased (p < 0.05) LS occurred in D350 vs. D100 (2.06 ± 0.2 vs. 1.36 ± 0.2); neither R nor D affected (p > 0.05; 38.5%) KIDD. However, EI, LAT, DUR, OR, and PREG were affected by the R × D interaction. The HSR group had the largest (p < 0.05) EI % and DUR h, irrespective of D. The shortest (p < 0.05) LAT occurred in D350, irrespective of R. While the largest (p < 0.05) OR occurred in HSR and MSR within D350, the HSR + D350 group had the largest PREG (p < 0.05). These research outcomes are central to defining out-of-season reproductive strategies designed to attenuate seasonal reproduction in goats.