Beef heifers with diminished numbers of antral follicles have decreased uterine protein concentrations

Authors: McNeel, Anthony; SOARES, EMERSON - Universidade Federal De Santa Maria; Patterson, Allyson; Vallet, Jeff; Wright, Elane; LARIMORE, ERIN - South Dakota State University; AMUNDSON, OLIVIA - South Dakota State University; Miles, Jeremy; Chase, Chadwick - Chad; Lents, Clay; WOOD, JENNIFER - University Of Nebraska; CUPP, ANDREA - University Of Nebraska; PERRY, GEORGE - South Dakota State University; Cushman, Robert - Bob

Submitted to: Animal Reproduction Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2017
Publication Date: 1/12/2017
Publication URL: https://handle.nal.usda.gov/10113/5613065
Citation: McNeel, A.K., Soares, E.M., Patterson, A.L., Vallet, J.L., Wright, E.C., Larimore, E.L., Amundson, O.L., Miles, J.R., Chase Jr., C.C., Lents, C.A., Wood, J.R., Cupp, A.S., Perry, G.A., Cushman, R.A. 2017. Beef heifers with diminished numbers of antral follicles have decreased uterine protein concentrations. Animal Reproduction Science. 179:1-9. doi: 10.1016/j.anireprosci.2017.01.004.

Interpretive Summary: Several studies have demonstrated that fertility and date of conception are decreased in cows with diminished numbers of follicles. One line of evidence suggests that uterine function may be compromised in these females. To test this hypothesis, a four-year study was performed with Angus heifers. Each year, a group of heifers were evaluated twice for antral follicle count, and after the second evaluation, the 10 pubertal heifers with the greatest number of antral follicles and the 10 pubertal heifers with the lowest number of antral follicles were sacrificed and the reproductive tract was collected. The heifers with low numbers of follicles had smaller uteri that produced less protein. There was no difference in the percent of endometrial area occupied by endometrial glands, the structures that produce uterine protein. From these results, we conclude heifers with diminished numbers of antral follicles have decreased uterine function that is a result of decreased ability of the uterine glands to produce or secrete protein. These data provide biological support for the improved fertility in heifers with increased numbers of antral follicles, and suggest that, if possible, it would be a good practice to screen recipients in an embryo transfer program to select those with increased numbers of follicles, because they are more likely to maintain the pregnancy.

Technical Abstract: Previous research demonstrated a favorable relationship between the number of follicles detectable in the bovine ovary by ultrasonography and fertility, and bovine females with diminished numbers of antral follicles had smaller reproductive tracts. Therefore, we hypothesized that uterine function would be compromised in beef heifers with diminished numbers of antral follilcles. Angus heifers (n = 480) were submitted for ultrasonographic evaluation of antral follicle number at 325 and 355 d of age. After the second ultrasonographic examination, the 39 pubertal heifers with the greatest number of antral follicles and the 40 pubertal heifers with the lowest number of antral follicles were synchronized with two i.m. injections of prostaglandin F2alpha (25 mg) administered 11 d apart, and heifers were slaughtered on d 6 or d 16 of the resultant estrous cycle. The uterus was weighed, flushed for determination of protein content, and representative pieces were fixed for determination of endometrial gland morphometry. Heifers in the Low group had fewer surface antral follicles and smaller reproductive tracts than heifers in the High group (P < 0.01). Protein content of the uterine flushes was decreased in heifers in the Low group (P < 0.01); however, there was no difference in the percent area of the endometrium occupied by endometrial glands (P > 0.30). From these results, we conclude that the uterine environment of beef heifers with diminished numbers of antral follicles is less conducive to supporting early embryonic survival.