128 Relationship between anti-Mullerian hormone (AMH) and reproductive traits in ewes

Abstract

Abstract Objective was to determine correlations between serum AMH and reproductive traits in ewes. Blood was collected at breeding from Katahdin ewes between 0.7 and 9 yr age in 2015 (n = 158) and 2017 (n = 233) for the analysis of serum AMH concentrations using different immunoassays (Equine and Ovine AMH in 2015 and Ovine AMH in 2017; AnshLab). Relationships between AMH and first exposure pregnancy rate (PR) to spring or fall breeding, number of lambs born to first lambing, age at first lambing (using lifetime records), and estimated breeding values (EBVs) for number of lambs born (NLB), number of lambs weaned (NLW), maternal weaning weight (MWT), weaning weight (WWT), and maternal index were determined. Correlations were determined using PROC CORR (SAS), and PROC GLM used with AMH or AMH quartile as dependent or independent variables, and season in models. Serum AMH or quartiles did not correlate with any reproductive trait. In 2017 but not 2015, AMH concentrations (P = 0.02) and quartiles (P = 0.04) were greater in ewes that became pregnant than nonpregnant ewes to first breeding. Ewes that were pregnant at a younger age had a higher WWT (P = 0.002), NLW (P = 0.04) and Index (P = 0.02), and more prolific ewes at first lambing had a higher NLB (P < 0.001), NLW (P < 0.001), and Index (P < 0.001), regardless of season of first breeding. Mean PR was -4.6 ± 3.8% and 68.4 ± 3.8% for spring and fall breeding (P < 0.001), resulting in older spring compared with fall bred ewes at first lambing (2.04 ± 0.08 vs. 1.52 ± 0.05 yr, P < 0.001). While AMH did not appear to consistently predict fertility in ewes, higher EBVs (NLB, NLW, Index) were associated with younger ewes and greater prolificacy at first lambing.