Delayed endometrial preparation for the induction of luteolysis as a potential factor for improved reproductive performance in Angus beef heifers with high antral follicle counts

Authors: KAPS, M - University Of Veterinary Medicine; QUAIL, LACEY - Texas Agrilife; ROSASCO, SHELBY - New Mexico State University; Snider, Alexandria - Alex; ZOCA, SAULO - South Dakota State University; EPPERSON, KAITLIN - Texas Agrilife; RICH, JERICA J - University Of South Dakota; Miles, Jeremy; Crouse, Matthew; Keel, Brittney; SUMMERS, ADAM - New Mexico State University; PERRY, GEORGE - Texas Agrilife; Lents, Clay; Cushman, Robert - Bob

Submitted to: Biology of Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Reproductive longevity in the cow herd contributes to profitability for beef producers. Ovarian ultrasonography is a technology that can be used to identify replacement beef heifers with greater fertility, but the physiological mechanisms contributing to this enhanced fertility are poorly understood. A study was performed to determine if there were differences in uterine function and embryonic development in beef heifers differing in numbers of ovarian follicles detectable by ultrasonography. There were no differences in early embryonic development, but heifers with increased numbers of follicles were more receptive to embryonic signals of pregnancy. These results indicate that there are uterine mechanisms contributing to enhanced fertility in heifers with greater numbers of follicles. There are several technologies available to cow-calf producers to identify these heifers, and cow-calf producers should consider using these technologies to improve the reproductive efficiency of their herd.

Technical Abstract: Antral Follicle Count (AFC) and anti-Müllerian hormone (AMH) concentrations are reflective for ovarian reserve and have been associated with improved reproductive performance in cattle. Key events for regulation of uterine receptivity are orchestrated by progesterone. As progesterone concentrations are greater in animals with high than low AFC, we tested the hypothesis, if the resulting improved uterine environment will lead to improved conceptus elongation and endometrial response to interferon tau. For four years, 10 heifers with lowest and highest AFC, respectively, were selected from 120 heifers. Reproductive tracts and blood samples for progesterone and AMH analysis were collected after synchronization and insemination. For a recovered conceptus, length was determined, and interferon tau (IFNT) transcript abundance was analyzed. Endometrial transcript abundance of interferon-stimulated gene 15 (ISG15) and oxytocin receptor (OXTR) were analyzed. Progesterone concentrations did not differ between Low and High AFC Group (P = 0.1). A difference in conceptus length was not observed. Endometrial abundance of ISG15 did not differ between Pregnant Low and High AFC heifers. Abundance of OXTR was greater in Open Low AFC than Open High AFC heifers (P < 0.01). Interaction of AMH and Pregnancy Status was determined, with greater AMH in Pregnant than Open High AFC heifers (P < 0.05). Improved uterine environment in High vs. Low AFC heifers did not result in longer conceptuses or improved endometrial response. As the increase in OXTR transcript abundance was only detected in Low AFC heifers, reported differences in reproductive performance might be associated with earlier initiation of luteolysis.