Endocrine Abstracts

JOINT1522

Bovine oogenesis and follicular maturation are initiated during in utero development, a process that is stringently orchestrated by the endocrine milieu. Of paramount importance are the three major biologically active estrogens: estron, estradiol, and estriol that are involved in the development and maintenance of germ cells. Previous work using the current model have revealed that maternal urea (protein precursor) supplementation reduces the ovarian follicular reserve without compromising the number of secondary and tertiary follicles. Therefore, we did not anticipate an influence of dietary treatment on biologically active estrogens. However, as the ovarian reserve is positively associated with circulating concentrations of anti-Mullerian hormone (AMH) we hypothesized that offspring from dams supplemented urea would have reduced circulating concentrations of AMH at birth. To characterize the effects of maternal urea supplementation, multiparous cows pregnant with female calves were individually-fed isocaloric dietary treatments consisting of chopped forage top-dressed with a control (0 g urea/animal/d) or urea (80 g urea/animal/d) pelleted supplement. Diets met or exceeded dietary requirements throughout gestation. Blood samples were collected from offspring at birth for the collection of plasma. Plasma was analyzed for concentration of estradiol, estrone, unconjugated estriol, and AMH using commercially available ELISA kits. The effect of maternal dietary treatment on concentration of hormones in offspring were evaluated by ANOVA. As expected, maternal dietary treatment did not influence circulating concentrations of estradiol (P = 0.41), estrone (P = 0.35), or unconjugated estriol (P = 0.31). However, it was not anticipated that maternal dietary treatment would have no effect on circulating concentrations of AMH (P= 0.97) as offspring of urea-supplemented dams had fewer primordial and primary follicles than offspring from control dams. From these results we infer that maternal urea supplementation induces precocious follicular activation and/or increases the number of follicles recruited during maturation through an AMH-independent mechanism. Moreover, these data illustrate that while offspring of dams offered urea throughout pregnancy have a reduction in primordial and primary follicles, the steroidogenic competence of secondary and tertiary follicles is no different than dams offered the control diet. USDA is an equal opportunity provider and employer.