Location: Livestock Bio-Systems
2023 Annual Report
Objectives
Objective 1. Establish the influence of nutrient intake during the peri-pubertal period on gamete quality in young beef animals.
Sub-objective 1.A: Determine if the stair-step development protocol results in increased circulating progesterone concentrations and improved uterine function in replacement beef heifers.
Sub-objective 1.B: Determine if differences in bull rate of gain during the peri-pubertal window influence the contributions of sperm to early embryonic development in-vitro and compare that to siring capacity in the pasture.
Objective 2. Determine the influence of nutritional supplements in vivo during follicle development and early pregnancy on fetal development and progeny performance.
Sub-objective 2.A: Determine if OmniGen-AF supplementation will increase circulating progesterone concentrations in beef heifers with diminished numbers of follicles.
Sub-objective 2.B: Determine if feeding OmniGen-AF to heifers for 50 days prior to the breeding season influences oocyte quality and blastocyst development.
Objective 3. Understand how specific nutrients provided directly to the embryo in vitro during the first seven days after fertilization contribute to proper embryonic development.
Sub-objective 3.A: Supplementing follistatin in combination with choline will increase in-vitro embryonic development.
Sub-objective 3.B: Determine if incorporating guanidinoacetic acid (GAA) and/or methionine during in-vitro embryo production alters blastocyst competence and development.
Objective 4. Apply remote sensors and related technologies for improved measurement of reproductive and production traits of cattle in rangeland and pasture settings.
Sub-objective 4.A: Develop techniques using geophysical mapping of soil spatial variability that can be used for precision grazing management of range beef cows.
Approach
As the world population continues to grow over the next 50 years, the demand for animal protein products to sustain human health will increase. The sustainable production of animal protein begins with efficient reproduction. Environment and management influence reproductive efficiency in beef cattle; therefore, better management practices by cow-calf producers will increase the reproductive efficiency of their herds. Nutritional status of the herd represents the component of the production system where management practices have the greatest overall impact on reproductive performance in the beef herd because nutrition influences onset of reproductive cycles, quantity and quality of male and female gametes, early embryonic development, maintenance of pregnancy, development of the progeny during pregnancy, and subsequent performance of those progeny after birth. Efforts in the last two project plans identified reproductive traits that predict fertility and implemented nutritional strategies to developmentally program those traits to improve reproductive efficiency. During this time, advancements in sensor technologies increased our ability to monitor reproductive performance and regulate nutrient intake, providing new possibilities for reproductive management in the beef herd. Applying results from our past accomplishments, the current project plan will improve strategies for developing heifers and bulls with the greatest quantity and quality of gametes possible (Objective 1), apply nutritional supplements that will improve deficiencies in reproductive traits in beef females with low fertility (Objective 2), use in-vitro embryo production technologies to explore nutritional strategies that will optimize embryo development (Objective 3), and use electronic sensor systems to assimilate real-time data on reproductive status of animals and nutrient availability of pastures to improve decision making in reproductive management of beef cattle on range (Objective 4). Results will provide cow-calf producers with tools to develop and manage highly fertile breeding stock that wean a greater number of calves at greater weights.
Progress Report
Objective 1: A Ph.D. student is being sought to take the lead on this study. The first cohort of heifers was identified after birth in spring 2023 and will go on trial in spring 2024 as per the timeline in the project plan.
Objective 2: The study was initiated and the first year of heifers were developed on the immunomodulatory supplement. Tissues were collected and are currently under-going laboratory analysis to determine if the supplement positively influences physiological mechanisms contributing to fertility in heifers with diminished numbers of follicles.
Objective 3: The experiment for Sub-objective 3A was initiated with oocytes treated with a control maturation media, maturation media containing follistatin, choline (1.3mM or 1.8mM) or a combination of choline and follistatin and examined for quality after maturation. Laboratory analysis was completed to determine oocyte quality with an abstract being presented at the American Society of Animal Science National Meeting. The next step of this experiment will be conducted this summer to determine early embryonic development from oocytes treated with choline, follistatin or a combination of both treatments. The experiment for Sub-objective 3B was initiated to determine the optimal dose of guanidinoacetic acid (GAA) suitable to supplement during oocyte maturation. An experiment was conducted with three different concentrations of GAA: 5mM, 10mM and 20mM and determined based on oocyte quality analysis after maturation that the 10mM dose was adequate for oocyte culture. The next steps of this experiment will be conducted to determine the impact of combining methionine with GAA during oocyte maturation and the subsequent impacts on oocyte quality and early embryonic development.
Objective 4: This is a new research project at Clay Center, Nebraska, and this is the first year of accomplishments. During 2018-2019, a Long-Term Agroecosystem Research (LTAR) site was established at Clay Center, Nebraska, as part of the Platte River-High Plans Aquifer LTAR investigating beef cattle and grassland systems. The initial design of the research site was limited due the size of the gas sampling area. During FY2022-2023, a redesign was proposed and approved to eliminate limitations of the current design and reduce the size to be comparable with the companion site in Mead, Nebraska. The new design will be a more effective collaborative site with the grazing research focus of the LTAR. It is anticipated the new design can be used as a baseline comparison for future planned precision grazing research in Clay Center, Nebraska. The second accomplishment was the identification of a new electromagnetic induction (EMI) sensor. Previous research at Clay Center, Nebraska, uses EMI sensors for developing field-scale precision management of land applied manure and precision feedlot surface management techniques. The new sensor simplifies use and application. Based on previous work, it is anticipated that the EMI data will be layered with additional site data and remote sensing instrumentation to develop a data driven approach for establishing boundaries of virtual fences for precision grazing of the pastures. Additionally, scientists at Clay Center, Nebraska, developed techniques using EMI sensors to provide field-scale spatial data on the impact of management on vegetative treatment systems designed to treat feedlot runoff wastewater. It is expected these techniques can be modified to use on pasture systems to prove similar information.
Accomplishments
1. Polymorphism of the follicle stimulating hormone receptor does not impact reproductive performance or in-vitro embryo production in beef heifers. Follicle stimulating hormone (FSH) is a key regulator for developing ovarian follicles, leading to ovulation of an oocyte for potential fertilization and can be used with assisted reproductive technologies. Recently, a genetic mutation in the receptor for FSH (FSHR) that influenced embryo quality during a superovulation protocol was identified. ARS researchers at Clay Center, Nebraska, conducted research to determine the utility of this mutation as a genetic marker of the ability of a cow to produce oocytes that are competent to produce embryos in-vitro. Results from this study showed that embryonic development rates did not differ between FSHR genotypes. This indicates that this FSHR genotype does not influence in-vitro embryonic development and may not aid in selecting superior females for use in in-vitro embryo production. While embryo transfer companies will market this genetic marker as a tool to identify fertile cows based on previous papers, these data show that cow-calf producers should be cautious when considering the expense.
2. Examining trans-generational impacts of maternal stress on daughter reproductive performance. Transporting cows by truck during pregnancy causes stress that negatively impacts the health and well-being of their offspring. ARS researchers at Clay Center, Nebraska, in collaboration with Texas AgriLife, Overton, Texas, conducted research to determine if transporting cows during pregnancy affected fertility of female progeny. Results demonstrated no negative impacts of transportation stress on ovarian development or fertility of female offspring over three generations. Cows that are pregnant with female calves can be transported safely by truck without negatively impacting reproductive performance of these female offspring. This becomes very important in times of drought when pregnant cows may need to be transported great distances to provide adequate forage.
3. Redesign of Long-Term Agroecosystem Research (LTAR) site. The Long-Term Agroecosystem Research site at Clay Center, Nebraska, was redesigned to improve measuring greenhouse gas emissions from grazing beef cattle. The new design will be used in conjunction with planned research developing applications of virtual fencing for precision grazing of beef cattle. Development of precision grazing of pasture systems by beef cattle will improve production efficiencies while improving soil health and pasture quality and resiliency.
4. Improving methods to evaluate fertility in bulls. Fifty percent of beef bulls that are diagnosed fertile at a pre-breeding examination fail to sire a significant number of calves. This costs U.S. beef producers $500 million a year in bull maintenance costs that are never recovered. ARS researchers at Clay Center, Nebraska, in collaboration with Texas AgriLife, Overton, Texas, identified proteins from seminal fluid that are associated with fertility in bulls. Two of these proteins were subjected to validation as biomarkers of fertility in bull semen by developing assays to characterize the abundance of the proteins in individual ejaculates. These proteins were measured in ejaculates from bulls that differed in fertility. There was no relationship between abundance of these proteins and fertility. Future efforts will focus on other proteins that were identified in the seminal fluid because beef producers need better methods to evaluate fertility in bulls.
5. Breeding soundness examinations of yearling bulls before and after a 28-day breeding season. Breeding soundness examinations are important for evaluating bulls prior to the breeding season, but bulls are not typically examined after a breeding season. Limited research investigated how breeding activity impacts breeding soundness over time. ARS researchers at Clay Center, Nebraska, conducted research to determine the impacts of a 28-day breeding season on yearling bulls. Results from this study demonstrated yearling bulls exposed to females had reduced sperm concentration and increased inflammatory cytokines within the seminal plasma after 28 days. This information provides insight on how fertility of yearling bulls changes throughout the breeding season, thus allowing producers to make decisions on the duration their bulls are in breeding pastures to optimize reproductive efficiency in the herd.
Review Publications
Zoca, S.M., Walker, J.A., Kline, A.C., Andrews, T.N., Rich, J.J.J., Epperson, K.M., Drum, J.N., Ortega, M.S., Cushman, R.A., Perry, G.A. 2023. Relationship of field and in vitro fertility of dairy bulls with sperm parameters, including DAG1 and SERPINA5 proteins. Frontiers in Animal Science. 4. Article 1180967. https://doi.org/10.3389/fanim.2023.1180967.
Zoca, S.M., Geary, T.W., Zezeski, A.L., Kerns, K.C., Dalton, J.C., Harstine, B.R., Utt, M.D., Cushman, R.A., Walker, J.A., Perry, G.A. 2023. Bull field fertility differences can be estimated with in vitro sperm capacitation and flow cytometry. Frontiers in Animal Science. 4. Article 1180975. https://doi.org/10.3389/fanim.2023.1180975.
Webb, E.M., Holman, D.B., Schmidt, K.N., Crouse, M.S., Dahlen, C.R., Cushman, R.A., Snider, A.P., McCarthy, K.L., Amat, S. 2023. A longitudinal characterization of the seminal microbiota and antibiotic resistance in yearling beef bulls subjected to different rates of gain. Microbiology Spectrum. 11(2). Article e05180-22. https://doi.org/10.1128/spectrum.05180-22.
Crouse, M.S., Freetly, H.C., Lindholm-Perry, A.K., Neville, B.W., Oliver, W.T., Lee, R.T., Syring, J.G., King, L.E., Reynolds, L.P., Dahlen, C.R., Caton, J.S., Ward, A.K., Cushman, R.A. 2023. One-carbon metabolite supplementation to heifers for the first 14 d of the estrous cycle alters the plasma and hepatic one-carbon metabolite pool and methionine-folate cycle enzyme transcript abundance in a dose-dependent manner. Journal of Animal Science. 101. Article skac419. https://doi.org/10.1093/jas/skac419.
Snider, A.P., Yake, H.K., Granger, C.D., Rosasco, S.L., McDaneld, T.G., Snelling, W.M., Chase Jr., C.C., Miles, J.R., Lents, C.A., Quail, L.K., Rich, J.J., Epperson, K.M., Crouse, M.S., Summers, A.F., Perry, G.A., Bennett, G.L., Cushman, R.A. 2023. Polymorphism of the follicle stimulating hormone receptor does not impact reproductive performance or in-vitro embryo production in beef heifers. Theriogenology. 195:131-137. https://doi.org/10.1016/j.theriogenology.2022.10.025.
Snider, A.P., McCarthy, K.L., Wright-Johnson, E.C., Ondrak, J.D., Oliver, W.T., Dahlen, C.R., Cushman, R.A., Crouse, M.S. 2022. Yearling bulls have reduced sperm concentration and increased seminal plasma interleukin-8 after a 28-day breeding season. Reproduction of Domestic Animals. 57:1465-1473. https://doi.org/10.1111/rda.14223.
Singh, A., Afzal, T., Woodbury, B.L., Wortmann, C., Iqbal, J. 2023. Alfalfa in rotation with annual crops reduced nitrate leaching potential. Journal of Environmental Quality. 52(3):930-938. https://doi.org/10.1002/jeq2.20473.
