Location: Livestock Bio-Systems
2022 Annual Report
Objectives
Objective 1: Apply developmental programming to improve production efficiency of beef cattle.
Objective 2: Improve swine production by identifying factors contributing to prenatal piglet development and survival and postnatal preweaning mortality.
Objective 3: Increase productivity and longevity of replacement gilts by identifying and defining physiological and environmental factors underlying developmental and reproductive processes.
Objective 4: Enhance sow performance and retention within the breeding herd by identifying physiological and environmental features at critical periods throughout life that contribute to production and longevity.
Objective 5 (new): Develop precision management technologies for livestock to automate measuring production traits.
Approach
Beef heifers that conceive early in their first breeding season have greater reproductive longevity and enhanced lifetime productivity. We reported that this is due, in part, to an increase in the number of antral follicles in their ovaries without any difference in Reproductive Tract Score or age at puberty. In the previous project period, we applied developmental programming (i.e., nutritional modifications at key stages of development) to heifers to increase the percentage that conceived early in their first breeding season and to increase the numbers of primordial follicles in their ovaries. The current project plan will determine if this resulted in increased reproductive longevity for these heifers and validate models that report the use of developmental programming to improve carcass characteristics in steer progeny (Objective 1). In Objective 2, we will investigate how nutrition and hormonal environment can impact the function of the genome during early embryonic development to better understand the factors contributing to fetal programming. In Objective 3, we will examine the maternal contributions to developmental programming by examining the influence of uterine function on conceptus development and the age of the dam on progeny performance. This research is critical to understand how early life events can impact adult traits and how we can harness developmental programming to improve the efficiency of beef production.
Progress Report
This is the final report for project 3040-31000-096-000D “Improving Livestock Production by Developing Reproductive and Precision Management Technologies”. This project will be replaced with project 3040-31630-001-000D in fiscal year (FY) 2023.
Objective 1: A series of studies were performed to understand how environmental and management factors such as nutrition and stress influenced performance. Maternal nutrition during early pregnancy impacted conceptus development and subsequent organ development in the fetus. Developmental programs applied in peri-pubertal heifers were demonstrated to improve ovarian function and increase lifetime productivity. The research carried out continues to elucidate the mechanisms involved in developmental programming so that it can be harnessed to enhance production efficiency of beef to deliver a healthy, safe, and economical commodity to the consumer.
Objective 2: Studies were conducted to understand how specific genetic polymorphisms in genes associated with growth and development (calpistatin, growth hormone) and genes associated with reproduction (follicle stimulating hormone receptor) influence reproductive function, hormonal profiles, and early embryonic development in beef heifers.
Objective 3: Studies were conducted to understand the influence of age of the dam on the size of ovarian reserve and reproductive performance of daughters. Daughters of mature cows had better ovarian development than heifers born to heifers, indicating that the best replacement heifers are produced by mature cows that have already proven their reproductive longevity. There was improved uterine function in heifers with greater numbers of follicles that led to enhanced conceptus development. Basic studies to understand how estradiol and progesterone influenced function of the oviduct and the uterus were conducted. Fertility is a difficult trait to quantify, but these studies provide opportunities to enhance management practices to increase fertility and productivity in the cow herd.
Accomplishments
1. Ovarian reserve influences uterine glucose concentrations in beef heifers. The uterus is the source of nutrients for the calf before the placenta forms. Glucose is the sugar that is the main source of energy for the calf during this time. ARS researchers at Clay Center, Nebraska, measured glucose in the uterus of young cows with different numbers of follicles. Cows with more follicles had more glucose in their uterus. The data provide mechanistic evidence for why using ultrasound to select cows with more follicles makes pregnancy more likely. This will assist beef farmers in selecting females to maximize reproduction in the herd.
2. Growth promoting implants can be used in heifers without damaging ovarian development. Growth promoting implants increase profits for beef producers. These implants damaged the reproductive organs (ovaries) of female calves when they were first placed on the market, but improvements were made to the drug delivery system. A collaboration between ARS researchers at Clay Center, Nebraska, and New Mexico State University showed that modern implants did not damage the ovaries of young cows. As a result, beef farmers can use implants in females without harming the ovaries. This allows beef farmers to use implants in females that will be bred and increases profits when females that fail to get pregnant are sold as beef.
3. Improving methods to diagnose fertility in beef bulls. Bulls receive a fertility exam before use in breeding herds. There are bulls that pass these exams but fail to sire any calves. ARS researchers at Clay Center, Nebraska, in collaboration with researchers at South Dakota State University, compared proteins in semen to select bulls that produce more calves. There were three proteins that differed in amount between bulls with high and low fecundity. These proteins will be used to develop new tools to evaluate fecundity in bulls. This will allow beef producers to use fewer bulls with better genetics and produce more beef of better quality.
4. Investigating contributions of uterine health to successful pregnancy in beef cows. Ninety-five percent of pregnancies in cows fail in the first two weeks. Cows with fertility problems typically have poor ovarian function and more uterine infections. ARS researchers at Clay Center, Nebraska, in collaboration with researchers at South Dakota State University, studied the role of uterine health in pregnancy failure and discovered that inflammation was more common in the uterus of cows with low fertility. A greater understanding of uterine health in beef cows is needed to improve reproductive well-being. These data provide researchers the base knowledge necessary to assess uterine status and develop new treatments for beef cows with uterine infections.
5. Increased follicular fluid androgens inhibit granulosa cell function in cows. Failure to ovulate reduces the number of cows pregnant and increases economic losses for beef farmers. ARS researchers at Clay Center, Nebraska, examined how androgen, a male sex hormone that also is present in females, in the follicular fluid affects function of the granulosa cells which are responsible for the growth and ovulation of the follicle. Treatment of granulosa cells with androgens inhibited proliferation of the cells. These results demonstrate why cows with increased androgen in their follicular fluid fail to ovulate. Researchers will need to develop tools to identify these cows and strategies to treat the condition to improve ovulation success.
Review Publications
Menegatti Zoca, S., Northrop-Albrecht, E.J., Walker, J.A., Cushman, R.A., Perry, G.A. 2022. Proteomic analyses identify differences between bovine epididymal and ejaculated spermatozoa that contribute to longevity. Theriogenology. 184:51-60. https://doi.org/10.1016/j.theriogenology.2022.02.021.
Cushman, R.A., Bennett, G.L., Tait, R.G., McNeel, A.K., Casas, E., Smith, T.P.L., Freetly, H.C. 2021. Relationship of molecular breeding value for beef tenderness with heifer traits through weaning of their first calf. Theriogenology. 173:128-132. https://doi.org/10.1016/j.theriogenology.2021.07.020.
Quail, L.K., Randel, R.D., Welsh Jr., T.H., Cushman, R.A., Yake, H.K., d'Orey Branco, R.A., Neuendorff, D.A., Long, C.R., Perry, G.A. 2022. Prenatal transportation stress did not impact ovarian follicle count for three generations of female Brahman offspring. Animal Reproduction Science. 243. Article 107016. https://doi.org/10.1016/j.anireprosci.2022.107016.
Snider, A.P., Crouse, M.S., Rosasco, S.L., Epperson, K.M., Northrop-Albrecht, E.J., Rich, J.J., Chase, C.C. Jr., Miles, J.R., Perry, G.A., Summers, A.F., Cushman, R.A. 2022. Greater numbers of antral follicles in the ovary are associated with increased concentrations of glucose in uterine luminal fluid of beef heifers. Animal Reproduction Science. 239. Article 106968. https://doi.org/10.1016/j.anireprosci.2022.106968.
Northrop-Albrecht, E.J., Rich, J.J., Cushman, R.A., Yao, R., Ge, X., Perry, G.A. 2022. Influence of conceptus presence and preovulatory estradiol exposure on uterine gene transcripts and proteins around maternal recognition of pregnancy in beef cattle. Molecular and Cellular Endocrinology. 540. Article 111508. https://doi.org/10.1016/j.mce.2021.111508.
Rosasco, S.L., Melchior-Tiffany, E.A., Kassetas, C.J., Cox, S.H., Dunlap, R.L., Hernandez Gifford, J.A., Scholljegerdes, E.J., Cushman, R.A., Summers, A.F. 2022. Effects of administration of a growth promoting implant during the suckling phase or at weaning on growth, reproduction, and ovarian development in replacement heifers grazing native range. Journal of Animal Science. 100(6):1-11. Article 170. https://doi.org/10.1093/jas/skac170.
