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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Nutrition and Environmental Management Research » Research » Publications at this Location » Publication #326121

Research Project: STRATEGIES TO IMPROVE HEIFER SELECTION AND HEIFER DEVELOPMENT

Location: Nutrition and Environmental Management Research

Title: Influence of ovarian reserves in beef heifers on uterine morphometry and function

Author
item Cushman, Robert - Bob
item Tenley, Sarah - University Of Nebraska
item Soares, Emerson - Universidade Federal De Santa Maria
item Mcneel, Anthony - Zoetis
item Chase, Chadwick - Chad
item Vallet, Jeffrey - Jeff
item Wood, Jennifer - University Of Nebraska
item Perry, George - South Dakota State University
item Cupp, Andrea - University Of Nebraska

Submitted to: Society for the Study of Reproduction Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/6/2016
Publication Date: 7/16/2016
Citation: Cushman, R.A., Tenley, S.C., Soares, E.M., McNeel, A.K., Chase, C.C., Vallet, J.L., Wood, J.R., Perry, G.A., Cupp, A.S. 2016. Influence of ovarian reserves in beef heifers on uterine morphometry and function [abstract]. Society for the Study of Reproduction Annual Meeting. Abstract #278 (Scientific Program p. 181).Available: http://www.ssr.org/sites/ssr.org/files/uploads/attachments/node/320/2016_ssr_abstracts.pdf

Interpretive Summary:

Technical Abstract: The size of the reproductive tract and the number of follicles in the ovaries are positively associated with fertility and early conception in beef heifers. Heifers with greater numbers of ovarian follicles have larger uteri that secrete a greater amount of protein on day 16 after estrus. Therefore, we hypothesized that this increase in uterine protein is associated with an increase in the percentage of the endometrium containing uterine glands in heifers with increased ovarian reserves. Angus heifers (n = 241) were submitted for ultrasonographic evaluation of the ovaries at 326.2 ± 1.0 and 355.8 ± 1.0 days of age. After the second ultrasonographic examination, the twenty pubertal heifers with the greatest number of antral follicles and the twenty pubertal heifers with the least number of antral follicles were synchronized with two shots of prostaglandin F2' (i.m.) administered 11 d apart, and slaughtered 16 d after the resultant estrus to harvest the reproductive tracts. The follicular fluid was aspirated from all follicles < 5 mm in diameter, pooled, and frozen for subsequent analysis of estradiol concentrations. A cross section of the ovary contra-lateral to the CL was fixed in 10% neutral buffered formalin and processed for histological evaluation of the ovarian reserve. A representative piece of endometrium contra-lateral to the CL was fixed in 10% neutral buffered formalin and processed for histological evaluation of uterine glands. Data were analyzed using GLM procedures with AFC group as a fixed effect. Uterine weights were greater in heifers with high numbers of follicles than heifers with low numbers of follicles (263.5 ± 9.8 vs.231.8 ± 9.8 g; P = 0.03). The number of surface antral follicles counted at slaughter was greater in heifers with high numbers of follicles than heifers with low numbers of follicles (70.4 ± 5.9 vs. 30.3 ± 5.9; P < 0.01). The number of primordial follicles per section was greater in heifers with high numbers of antral follicle count than heifers with low numbers of antral follicle count (75.2 ± 8.8 vs. 45.6 ± 8.8; P < 0.01), demonstrating that ultrasonography was an effective method of estimating the size of the ovarian reserve in beef heifers. Follicular fluid E2 did not differ between heifers with high or low numbers of follicles (1.2 ± 0.6 vs. 1.6 ± 0.6 ng/ml; P = 0.61). Contrary to the hypothesis, the percent of the endometrium containing uterine glands did not differ between heifers based on size of the ovarian reserve (High = 15.2 ± 0.7, Low = 14.8 ± 0.7 percent; P = 0.71). From these results, we conclude that the increase in uterine protein in heifers with increased ovarian reserves is not due to an increase in the percent of the endometrium containing uterine glands and may instead be due to increased activity of secretory portals.