Ovarian hormones AMH and E2 in juvenile gilts as markers of reproductive success

Abstract

In Australia, only around 60% of gilts being retained to parity three. This is concerning as gilts do not reach optimal reproductive performance until parity three. Reproductive inadequacy is the main contributing factor for this premature culling. Thus, the traditional process for selecting breeding gilts is inadequate. Circulating oestradiol (E2), Anti-Müllerian hormone (AMH) and hormonal profiles in response to gonadotropin stimulation have been linked with reproductive potential in species other than pigs. This thesis aimed to determine the serum E2 and AMH levels in juvenile gilts prior to and after gonadotrophin stimulation and assess their associations with fertility and reproductive performance to determine their use as a selection tool for gilts with greater reproductive success. Experiment One examined serum AMH and E2 levels in juvenile gilts 0, 2 and 4 days after gonadotropin stimulation versus mating, litter and culling information for three parities. Experiment Two assessed whether juvenile levels of E2 and AMH were associated with ovarian and uterine properties at 160 days. Experiment One was repeated at two geographically different farms in Experiment Three. The final experiment was similar to Experiment two but was longitudinal and involved a more detailed ovarian assessment. To our knowledge, quantification of AMH in juvenile gilts in this thesis was novel. Results showed serum AMH to be negatively associated with ovarian follicle numbers but the association with uterine properties was inconsistent. A negative association between E2 and future litter numbers was also found. Whether serum AMH and E2 levels in juvenile gilts are associated with uterine traits requires further investigation. The results highlight the complexities of endocrinology, emphasising the difficulty of determining hormonal markers for reproductive potential in a production setting.