Location: Reproduction Research2019 Annual Report
1a. Objectives (from AD-416):
Objective 1: Apply developmental programming to improve production efficiency of beef cattle. Sub-objective 1.A: Apply fetal programming to improve progeny performance. Sub-objective 1.B: Apply nutritional programming in the peri-pubertal period to improving performance. Objective 2: Identify genetic and epigenetic mechanisms that contribute to early embryonic development. Sub-objective 2.A: Determine the influence of resveratrol on early embryonic development. Sub-objective 2.B: Determine the influence of non-esterified fatty acids on early embryonic development in cows differing in antral follicle number. Sub-objective 2.C: Determine the influence of a loss of function polymorphism in the follicle stimulating hormone receptor gene on cumulus cell function and early embryonic development. Objective 3: Identify maternal contributions to progeny performance. Sub-objective 3.A: Identify contributions of uterine proteins to conceptus development in beef heifers differing in antral follicle number. Sub-objective 3.B: Determine the influence of age of dam on progeny performance.
1b. Approach (from AD-416):
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.
3. Progress Report:
Calf performance measurements were collected for experiments in Objectives 1 and 3. Studies were completed examining the influence of non-esterified fatty acids on early embryonic development in vitro (Objective 2B). Initial results indicate that stearic acid inhibits blastocyst development, and that there are no differences in response to stearic acid between cows with increased numbers of follicles and cows with diminished numbers of follicles. This may imply that all advantages to fertility in heifers with increased numbers of follicles are due to a more supportive uterine environment. The second year of data collection was completed to examine the influence of a polymorphism in the FSH receptor on early embryonic development in vitro (Objective 2C). The data for the first year were collected for Objective 3A, examining conceptus development in heifers that differ in antral follicle number. Preliminary data indicate that conceptuses are shorter and conception rates are decreased in heifers with diminished numbers of follicles.
1. Influence of cow age on daughter reproductive performance. Pregnancy loss costs the beef industry more than $85 million annually. ARS researchers at Clay Center, Nebraska, in collaboration with South Dakota State University, New Mexico State University, and the University of Nebraska demonstrated that heifers born to mature cows had better development of the ovaries and reproductive tract than heifers born to heifers. These results indicate that selecting replacement heifers from mature cows will improve the overall reproductive performance of the herd. These data further indicate that applying nutritional treatments to a pregnant cow to control health, growth, and fertility of her offspring may have responses that differ depending on the age of that cow.
2. Cow nutrient status during pregnancy decreases function of metabolic pathways in the calves. Nutritional status of the mother during early pregnancy can alter the health, growth, and fertility of her offspring. Calves that become sick or do not grow well constitute an economic loss for producers. An ARS researcher at Clay Center, Nebraska, collaborated with researchers at North Dakota State University to investigate the influence of decreased nutrient intake during the first 50 days of pregnancy on function of liver, muscle, and brain in calves. The results demonstrated that decreased maternal nutrient intake inhibited metabolic pathways in the fetuses in ways that are predicted to decrease the growth trajectories of the calves after birth. These pathways will provide targets for pharmaceuticals or feed supplements that will improve health, growth, and fertility of the calves.
3. Investigating differences in ovarian function between Bos indicus and Bos taurus cows. Bos indicus cattle are better adapted to the environment of the southern United States; however, decreased fertility is a major factor in these cattle that limits their utility in production systems. ARS researchers at Clay Center, Nebraska, in collaboration with New Mexico State University and South Dakota State University identified differences in ovarian function between Bos indicus and Bos taurus cows. Brangus cows, which are only 37.5% Bos indicus, had ovaries that were like full-blooded Bos indicus cows. These differences in ovarian function due to biological type indicate that there are differences in the genetic pathways involved in ovarian development and function. Understanding these differences will aid in improving reproductive management of Bos indicus cows.
Tenley, S.C., Spuri Gomes, R., Rosasco, S.L., Northrop, E.J., Rich, J.J., McNeel, A.K., Summers, A.F., Miles, J.R., Chase, Jr., C.C., Lents, C.A., Perry, G.A., Wood, J.R., Cupp, A.S., Cushman, R.A. 2019. Maternal age influences the number of primordial follicles in the ovaries of yearling Angus heifers. Animal Reproduction Science. 200:105-112. https://doi.org/10.1016/j.anireprosci.2018.12.004.
Santa Cruz, R., Cushman, R.A., Vinoles, C. 2018. Antral follicular count is a tool that may allow the selection of more precocious Bradford heifers at weaning. Theriogenology. 119:35-42. https://doi.org/10.1016/j.theriogenology.2018.06.010.
Northrop, E.J., Rich, J.J., Cushman, R.A., McNeel, A.K., Soares, E.M., Brooks, K., Spencer, T.E., Perry, G.A. 2018. Effects of preovulatory estradiol on uterine environment and conceptus survival from fertilization to maternal recognition of pregnancy. Biology of Reproduction. 99(3):629-638. https://doi.org/10.1093/biolre/ioy086.
Cushman, R.A., Perry, G.A. 2019. Developmental programming of fertility in livestock. Veterinary Clinics of North America. 35(2):321-330. https://doi.org/10.1016/j.cvfa.2019.02.003.
Crouse, M.S., Caton, J.S., Cushman, R.A., McLean, K.J., Dahlen, C.R., Borowicz, P.P., Reynolds, L.P., Ward, A.K. 2019. Moderate nutrient restriction of beef heifers alters expression of genes associated with tissue metabolism, accretion, and function in fetal liver, muscle, and cerebrum by day 50 of gestation. Translational Animal Science. 3(2):855-866. https://doi.org/10.1093/tas/txz026.