Relationship of Anti-Mullerian Hormone to Reproductive Traits in Katahdin Ewes Bred in Late Spring or Fall

Abstract

Anti-Mullerian hormone (AMH) is an endocrine marker for fertility in many species. This study investigated possible correlations between serum AMH concentrations, mean number of lambs born (out-of-season in spring or fall), and estimated breeding values (EBVs) for number of lambs born (NLB), number of lambs weaned (NLW), maternal weaning weight (MWWT), weaning weight (WWT), and maternal index (determined by Sheep Genetics Australia). Blood was collected at breeding from Katahdin ewes between 0.7 and 7 years of age in 2015 (n = 163) for the analysis of serum concentrations of AMH. Anti-Mullerian hormone concentration was either expressed quantitatively or divided into quartiles (AMH Q1 through Q4, with Q1 the lowest and Q4 the highest, pg/ml). Data were analyzed by PROC CORR, GLM or chi-squared using SAS. Mean serum AMH was 182 ± 11 pg/ml and ranged from 0 to 1112 pg/ml. There was no correlation between serum AMH and EBVs for NLB, NLW, MWWT, WWT and the maternal index. Serum AMH concentration was similar in ewes in different age categories (P = 0.157). There was a correlation between EBV for NLB (0.29; P = 0.0002) and NLW (0.19; P = 0.013) with average number of lambs born. Ewes in the lowest AMH quartile (Q1) had a lower mean number of offspring born from spring breeding compared with ewes in other AMH quartiles (Q2, Q3, and Q4; P < 0.05). Further study is needed to determine the effectiveness of using serum AMH for selecting ewes for out-of-season (spring) breeding.