Modulation of expression of estrus, steroidogenesis and embryo development following peri-Artificial Insemination nutrient restriction in beef heifers

Authors: EPPERSON, KAITLIN - Texas A&M University; BECK, ERIN - South Dakota State University; RICH, JERICA - Arkansas State University; NORTHROP-ALBRECHT, EMMALEE - South Dakota State University; PERKINS, STEPHANIE - South Dakota State University; Zezeski, Abby; KETCHUM, JACLYN - Texas A&M University; ZOCA, SAULO - South Dakota State University; WALKER, JULIE - South Dakota State University; Geary, Thomas; PERRY, GEORGE - Texas A&M Agrilife

Submitted to: Animal Reproduction Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2022
Publication Date: 7/26/2022
Citation: Epperson, K.M., Beck, E.E., Rich, J.J., Northrop-Albrecht, E.J., Perkins, S.D., Zezeski, A.L., Ketchum, J.N., Zoca, S.M., Walker, J.A., Geary, T.W., Perry, G.A. 2022. Modulation of expression of estrus, steroidogenesis and embryo development following peri-Artificial Insemination nutrient restriction in beef heifers. Animal Reproduction Science. 244. Article 107045. https://doi.org/10.1016/j.anireprosci.2022.107045.
DOI: https://doi.org/10.1016/j.anireprosci.2022.107045

Interpretive Summary: Heifer calves developed for herd replacements are often developed one of two ways. The first way is to develop heifers in a feedlot where feed is provided daily. The second is to place the heifers on range where they graze for feed. Heifers are often bred by artificial insemination (AI) to ensure calving ease. Breeding season usually begins during late spring when nutrients and/or forage may be limited. Heifers developed on range can receive poor nutrition before and after AI when range conditions are poor. Heifers developed in a feedlot can receive poor nutrition when taken to pasture after AI. Egg development and fertility could be decreased by poor nutrition before AI. Embryo development could be decreased by poor nutrition after AI. Effects of energy restriction before and after AI were studied here. Poor nutrition before AI decreased key hormone levels and also delayed embryo development. Poor nutrition after AI reduced embryo quality. Results from this study highlight the need to provide adequate nutrition to heifers before and after AI to increase reproductive success.

Technical Abstract: Nutritional changes immediately after insemination can result in increased embryonic mortality, but the mechanisms controlling this are not well known. Our objective was to evaluate the impact of nutritional change on estrus expression, steroid concentrations, peripheral and uterine luminal fluid metabolites, and embryo quality in beef heifers. In multiple replications over two years, heifers (n=139) were assigned to one of two pre-artificial insemination (AI) dietary treatments: LOW or HIGH. LOW heifers were provided =90% NEm, while HIGH heifers were provided =139% NEm. Heifers remained in their respective treatments for 33 to 36 days. At time of AI (d0), half of the heifers in each treatment were randomly reassigned treatment to generate four pre- by post-AI treatments; HIGH-HIGH, HIGH-LOW, LOW-HIGH, and LOW-LOW. Heifers remained in their new diet treatment until embryo collection occurred on d6/7. Negative energy balance was achieved among LOW heifers as demonstrated by body weight loss and increased NEFA concentrations (P<0.05). Pre-AI treatment influenced expression of estrus (P=0.02; HIGH 83.6±5.2% vs. LOW 66.1±5.3%). Estradiol concentrations and interval to estrus were not affected by treatment (P>0.76); however, progesterone concentrations were reduced among LOW pre-AI heifers compared to HIGH (3.53±0.38, 4.85±0.37 ng/mL, respectively; P=0.02). Treatment prior to AI influenced embryo stage (P = 0.05; HIGH 3.61±0.32 vs. LOW 2.72±0.30). Post-AI treatment affected embryo grade (P=0.02; HIGH 1.78±0.23 vs. LOW 2.64±0.27). In summary, nutrient restriction prior to AI resulted in decreased expression of estrus, reduced progesterone concentrations after AI, and negatively impacted embryo development, while restriction after AI hindered embryo quality.