Skip to main content
ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Livestock Bio-Systems » Research » Publications at this Location » Publication #399187
Research Project: Applying Nutritional Strategies to Improve Early Embryonic Development and Progeny Performance in Beef Cows

Location: Livestock Bio-Systems

Title: An extreme model of fertility in sheep demonstrates the basis of controversies surrounding antral follicle count and circulating concentrations of anti-Müllerian hormone as predictors of fertility in ruminants

Author
item Cushman, Robert - Bob
item Yake, Hannah
item Snider, Alexandria - Alex
item Lents, Clay
item Murphy, Thomas - Tom
item Freking, Bradley - Brad

Submitted to: Animal Reproduction Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2023
Publication Date: 10/29/2023
Citation: Cushman, R.A., Yake, H.K., Snider, A.P., Lents, C.A., Murphy, T.W., Freking, B.A. 2023. An extreme model of fertility in sheep demonstrates the basis of controversies surrounding antral follicle count and circulating concentrations of anti-Müllerian hormone as predictors of fertility in ruminants. Animal Reproduction Science. 259. Article 107364. https://doi.org/10.1016/j.anireprosci.2023.107364.
DOI: https://doi.org/10.1016/j.anireprosci.2023.107364

Interpretive Summary: Females with fewer follicles in their ovaries have poor fertility. Ultrasonography to count follicles or measurement of anti-Müllerian hormone in the blood are tools to estimate the number of follicles. In a study at the U.S. Meat Animal Research Center, eighty-seven percent of ewes diagnosed infertile by counting follicles were infertile and number of follicles correctly identified 68% of the infertile ewes. One hundred percent of the ewes diagnosed infertile by anti-Müllerian hormone were infertile, but anti-Müllerian hormone only correctly identified 58% of the infertile ewes. The anti-Müllerian hormone assay is ten times more expensive than ultrasonography. Currently, ultrasonography provides sheep producers the most efficient and cost-effective method for identifying and culling ewes with poor fertility.

Technical Abstract: Ovarian ultrasonography and measurement of circulating concentrations of anti-Müllerian hormone (AMH) have been used to estimate follicle number and predict fertility in mammalian females, but no study has evaluated follicle number and circulating concentrations of AMH in ewes known to differ in fertility. We tested the hypothesis that ewes that had failed to lamb (BARREN) in four consecutive annual breeding seasons of 21 to 35 d have fewer follicles and diminished circulating concentrations of AMH compared to closely matched ewes that consistently produced lambs (FERTILE) under the same breeding protocols. Once identified, BARREN ewes (n = 19) were paired by breed and sire to a FERTILE control ewe (n = 19) and reproductive tracts were recovered at necropsy. Visible antral follicles in both ovaries were counted and a representative cross section of one ovary was embedded for histological evaluation of pre-antral follicle numbers. Paired t-tests indicated that BARREN ewes had fewer antral follicles, fewer primordial follicles, and decreased circulating concentrations of AMH compared to FERTILE ewes (P = 0.01), but there were ewes in each fertility classification that had ovarian phenotypes like the opposite fertility classification. The best technologies we have currently for estimating follicle numbers are ultrasonography and measurement of circulating concentrations of AMH, but no single technique is perfect for predicting fertility. A better understanding of the under-lying biological mechanisms linking AMH, folliculogenesis, and fertility is required to improve the use of measurements of follicle number for predicting fertility in livestock.