PSIV-11 Maternal nutrient restriction effects on Anti-Mullerian hormone and puberty attainment in beef heifers.

Abstract Maternal nutrition during mid-gestation plays a crucial role in the development of the reproductive system in cattle, particularly in the migration of primordial germ cells and the formation of female ducts and ovaries (Senger, P.L. 2012). Nutrient restriction during this period may lead to decreased fertility due to nutrient prioritization for vital organs relative to reproductive systems. This study aims to determine how maternal nutrient restriction during the second trimester of gestation affects the reproductive potential of female offspring by evaluating puberty attainment and plasma Anti-Mullerian Hormone (AMH) concentration. AMH is a blood marker for ovarian reserve and allows for determining reproductive potential in heifers. We hypothesize that nutrient restriction during mid-gestation will negatively impact the ovarian reserve of female offspring by disrupting primordial germ cell migration. Bos Taurus cows of Angus crosses were subjected to nutrient restriction during 95 days of mid-gestation at the SDSU Cottonwood Research Station, resulting in a loss of 1 body condition score (BCS). Heifer calves (n=16) were born from cows that maintained a BCS of 5 (control, PES, n=8), and cows that lost 1 BCS during mid-gestation (NES, n=8). At weaning (average 24 weeks of age), blood samples were collected and evaluated for AMH plasma concentration using AMH (Bovine) ELISA (AnshLabs, Webster, TX). After weaning, calves were backgrounded for 90 days and transferred to the Cow-Calf Education and Research Facility (CCERF – SDSU), where they were fed a standard finishing ration and evaluated weekly for puberty attainment via transrectal ultrasonography. Puberty was defined by the presence of a corpus luteum (CL) on ultrasound. At weaning (average 24 weeks of age) there was no significant difference between the AMH concentrations in the plasma of PES and NES heifers (P=0.15). Two heifers, both from the NES group, have attained puberty via transrectal ultrasonography at week 3. However, we plan to evaluate AMH concentrations in the plasma of PES and NES heifers at puberty, as it is a more representative indicator of future ovarian reserve (Hossam, et al. 2017). In conclusion, this study demonstrated that the AMH concentration at weaning was not affected by the restriction in utero. While no significant differences have been observed so far, the ongoing evaluation of puberty attainment and AMH at puberty may offer a clearer understanding of the impact restriction may have on the reproductive potential of heifers.