Anti-mullerian hormone as a predictive endocrine marker for selection of White Dorper ewe lambs at prepubertal age

Abstract

Identifying early puberty in ewe lambs is an important strategy to improve reproductive performance and economic results of sheep herd. The anti-Müllerian hormone (AMH) has become the main endocrine marker for the ovarian reserve of growing follicles in several mammal species. This study aimed to evaluate plasma anti-Müllerian hormone (AMH) levels in 32 prepubertal ewe lambs and their relationship with fertility in the breeding season at 12 months of age. AMH levels and presence of ovulation (corpus luteum - CL) were evaluated at 120, 150, and 180 days of age in 32 prepubertal White Dorper ewe lambs 6 days after the exogenous administration of a single dose of eCG (600 IU). The results showed that plasma AMH levels were similar in prepubertal ewe lambs regardless of age. Ovulation rates was influenced by age (P = 0.04), but not by the plasma concentration of AMH and live weight (P > 0.10). Thirteen ewe lambs from the 32 were intended to breeding, based on recommended minimum weight and body condition score (BCS) for first breeding, and exposed to the ram at 12 months of age to study the relationship between prepubertal AMH concentration and occurrence of pregnancy. Pregnant ewes were the ones with higher concentrations of AMH measured at 150 and 180 days of age (P = 0.064, 150 days; P = 0.014, 180 days) compared to the non-pregnant ones. On the other hand, pregnant and non-pregnant ewes showed no difference (P = 0.84) for AMH concentration determined at 120 days of age. Therefore, we conclude that plasma concentration of AMH at prepubertal age is reliable endocrine marker for the early identification of ewe lambs' reproductive activity and can be used as a tool for selecting fertile females.