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United States Department of Agriculture

Agricultural Research Service

Research Project: STRATEGIES TO IMPROVE HEIFER SELECTION AND HEIFER DEVELOPMENT

Location: Nutrition and Environmental Management Research

Title: How our basic understanding of the ovarian reserve is improving reproductive management in domestic farm animals

Authors
item Cushman, Robert
item McNeel, Anthony
item Chase, Chadwick
item Lents, Clay

Submitted to: Midwestern Section of the American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: December 19, 2012
Publication Date: March 1, 2013
Citation: Cushman, R.A., McNeel, A., Chase, C., Jr., Lents, C. 2013. How our basic understanding of the ovarian reserve is improving reproductive management in domestic farm animals [abstract]. Journal of Animal Science. 91 (Supplement 2):77-78 (Abstract #O237).

Technical Abstract: Mammalian females are born with a finite number of oocytes in their ovaries, the majority of which are stored as dormant primordial follicles. This finite supply of female gametes, termed the ovarian reserve, is established before birth and slowly depletes through the processes of follicle activation, recruitment, selection, and atresia until reproductive senescence occurs. While most females of domestic farm species do not remain in the production herd long enough to reach reproductive senescence, research focused on the ovarian reserve has made it clear that variations in the ovarian reserve that are present at birth affect many aspects of reproductive function. This variation in follicle numbers directly contributes to the variation in response to multiple ovulation embryo transfer (MOET) protocols because there are positive correlations between the numbers of preantral follicles and the numbers of antral follicles. However, in Bos indicus cows, the number of antral follicles detectable by ultrasonography is increased without a corresponding increase in the number of preantral follicles or an increase in ovulation rate, suggesting that mechanisms that enhance secondary to antral follicle transition cause this increase. The number of ovarian follicles is positively associated with reproductive tract development in replacement females. In gilts, selection for increased uterine capacity resulted in an increased number of antral follicles without any differences in the numbers of preantral follicles. Antral follicle numbers are positively associated with fertility. This is due to a positive relationship between follicle number and oocyte competence because in 4-month-old heifers, in vitro fertilization rates were positively associated with follicle numbers. Evidence from aged cows indicates that depletion of the ovarian reserve can alter reproductive function and influence length of productive life. Application of this information has improved selection decisions and assisted reproductive technologies in farm species. USDA is an equal opportunity provider and employer.

Last Modified: 7/25/2014