Advancing the health and well-being of animals and people


Principal Investigator: Joanne Fortune

Department of Biomedical Sciences
Email: jf11@cornell.edu; Phone: 607-253-3466
Sponsor: USDA NIFA-Hatch/Multistate Federal Formula Funds
Grant Number: NYC-435801
Title: Ovarian Influences on Reproductive Success in Ruminants
Project Amount: $120,000
Project Period: 10/01/13-09/30/17

DESCRIPTION (Provided by Applicant): Impaired reproductive performance is a major cause of reduced productivity of ruminants and reduced profitability for dairy and meat producers. The focus of our previous Multistate Projects (NE-1027, -1007 and -161) was nutritional, management, and environmental factors that impact ovarian activity and subsequent pregnancy rates in domestic ruminants. Our current goal is to continue this important investigative work. Our part of the current Multistate Project (NE-1227) is to study the role of the steroid hormone estrogen in the formation and initial growth of ovarian follicles in cattle. In the ovaries of mammals, the ovarian follicle is the unit of structure and function. Follicles contain one oocyte (future egg cell) and many follicle cells, which provide support to the oocyte and make hormones that affect other parts of the body to facilitate reproduction. In cattle, ovarian follicles form in the fetus and there is evidence that the number that form may influence the fertility of the individual when she becomes an adult and thus have economic impact for dairy framers and ranchers. We have developed methods for studying follicle formation and the initiation of follicle growth (follicle activation) in organ ulture. We found that an estrogen, 17beta-estradiol (E2), inhibits follicle formation and competence of follicles to activate in culture. It is known that the developing fetal bovine ovary synthesizes E2 and has at least two receptors for it. Our objective is to test the hypothesis that E2 exerts its regulation of follicle formation and activation by acting through the ERα and/or ERβ receptors. This will be a first step to uncover the pathways by which estradiol affects follicle formation and activation. We will culture pieces of bovine ovaries with or without agonists (compounds that mimic estradiol) or antagonists of one or both of the E2. At the end of culture, the ovarian pieces will be fixed and tissue sections will be prepared and examined to determine the effects of the agonists/antagonists on follicle formation and activation. There is some evidence that the number of follicles formed affects fertility later in life and also indirect evidence that estrogenic compounds present in the feed or the environment can affect the number of follicles formed. This basic information about how the fetal ovary is regulated in cattle is necessary so that future studies can address the question of how steroid production can be optimized to produce females that have high numbers of ovarian follicles and thus have higher reproductive potential. For example, factors like nutrition and exposure of cattle to feed and environmental factors that have estrogen-like activity may impact steroid production and/or directly affect follicle formation and growth. Knowledge of how follicle formation is regulated may be used in the future to increase the size of follicle pool (correlated with adult fertility). Estrogenic compounds in feed and in the environment may negatively impact follicle formation and the proposed research could lead to a better understanding of how they act on the fetal ovary. NY has a major dairy industry which could be aided by practical applications from such findings.