Location: Livestock Bio-Systems2018 Annual Report
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.
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.
Calf performance measurements were collected for experiments in Objectives 1 and 3. Experiments were conducted to investigate the influence of resveratrol on early embryonic development in vitro (Objective 2A). These results demonstrated that treatment with resveratrol may alter the epigenome in these embryos and change the transcript abundance of genes involved in fatty acid metabolism. Studies were initiated to examine 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. The first 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).
1. Cows that demonstrate behavioral estrus during a timed artificial insemination protocol are more fertile than cows that do not demonstrate behavioral estrus. ARS researchers at Clay Center, Nebraska, in collaboration with South Dakota State University, tested the hypothesis that early embryonic mortality was greater in cows that did not demonstrate behavioral estrus. Results of this study showed that there was no difference in embryonic survival to day 16 of pregnancy between cows that demonstrated behavioral estrus and cows that did not, indicating that embryonic loss in cows that do not display behavioral estrus occurs after day 16 of pregnancy. Uterine flushes from pregnant cows had 131% greater protein concentrations and 4% greater glucose concentrations than uterine flushes of non-pregnant cows; however, there was no difference in protein concentrations or glucose concentrations between cows that did or did not demonstrate behavioral estrus. Serum estradiol concentrations were three times greater in cows that demonstrated behavioral estrus. These results indicate that the estradiol does not alter the uterine environment but may influence development of the embryo directly. While there is no difference in embryonic development to day 16, pregnancy at day 35 is decreased in cows that do not demonstrate behavioral estrus. Therefore, estradiol may program changes in the embryo before day 16 that result in greater survival between day 16 and day 35 of pregnancy. Improving synchronization protocols to increase the number of cows that demonstrate behavioral estrus will increase pregnancy rates. Increasing the efficiency of these protocols will lead to greater adoption of the technology by cow-calf producers.
2. Identifying predictors of heifer fertility that can be measured at weaning. Research has shown that calving early as a heifer increases lifetime productivity and reproductive longevity. It is also known that heifers with greater numbers of follicles conceive earlier in their first breeding season. Although antral follicle count has been demonstrated to be highly repeatable within heifer after a year of age, the repeatability of follicle counts between weaning and first breeding has not been studied. ARS researchers at Clay Center, Nebraska, in collaboration with researchers from Uruguay determined the repeatability of antral follicle count between weaning and first breeding in Braford and Hereford heifers, and examined the relationship of antral follicle count with growth traits and age at puberty. In Braford heifers, there was a favorable relationship between antral follicle number and age at puberty, such that heifers with increased numbers of follicles attained puberty earlier, but there was not a relationship between follicle number and age at puberty in Hereford heifers. Heifers from both breeds with greater numbers of follicles had increased rates of growth and greater serum progesterone concentrations following artificial insemination. These results indicate that antral follicles can be counted by ultrasonography at weaning to aid in the selection of replacement heifers; however, the positive influence of antral follicle count on puberty may only exist in Bos indicus influenced cattle.
3. Investigation of the biological pathways to improve synchronization of estrus in beef cows. Synchronization of estrus increases efficiency of artificial insemination because detection of estrus is easier when large groups of cows demonstrate behavioral estrus at the same time and labor can be concentrated into a shorter breeding season. Improper response to the hormone that causes regression of the corpus luteum, prostaglandin F2alpha (PGF2alpha), can cause inefficiencies in synchronization of estrus for producers. ARS researchers at Clay Center, Nebraska, in collaboration with the University of Nebraska, examined the biological pathways activated in the bovine corpus luteum immediately after administration of PGF2alpha. Genes involved in stimulation of immune cells were activated immediately after administration of PGF2alpha. This immune response is required to drive regression of the corpus luteum to completion. Understanding the failure of this immune response mechanism in some cows will improve the efficiency of synchronization of estrus. Increased use of artificial insemination in the beef industry will improve efficiencies and generate more rapid genetic improvement for producers.
4. Assessing objective indicators of stress in beef cattle. Animal productivity may be limited by the inherent stress within a production system; for example, stressors associated with common practices such as weaning, processing, or transportation. Cortisol concentration is often used to assess stress. Temperament is also an important trait that can be objectively measured to assess stress in beef cattle. ARS researcher at Clay Center, Nebraska, evaluated calves from diverse breeds (Angus, Brahman, and Romosinuano and their crosses) for stress and temperament at weaning and transport. There were no breed differences in cortisol, indicating similar stress responses at weaning and at transport across breeds. Temperament assessed using exit velocity, indicated that temperament did not differ between Brahman and Brahman crosses, or between Angus and Romosinuano or Brahman crosses. These results suggest that stress under typical production practices elicits a cortisol response that is similar among diverse breeds. For the assessment of temperament, exit velocity offers producers an objective assessment of temperament that if conducted at weaning could allow selection of replacement animals with favorable temperaments and improved productivity.
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Talbott, H., Hou, X., Qui, F., Zhang, P., Guda, C., Yu, F., Cushman, R.A., Wood, J.R., Wang, C., Cupp, A.S., Davis, J.S. 2017. Transcriptomic and bioinformatics analysis of the early time-course of the response to prostaglandin F2 alpha in the bovine corpus luteum. Data in Brief. 14:695-706. https://doi.org/10.1016/j.dib.2017.08.026.
Britt, J.H., Cushman, R.A., Dechow, C.D., Dobson, H., Humblot, P., Hutjens, M.F., Jones, G.A., Ruegg, P.S., Sheldon, I.M., Stevenson, J.S. 2018. Invited review: Learning from the future--A vision for dairy farms and cows in 2067. Journal of Dairy Science. 101(5):3722-3741. https://doi.org/10.3168/jds.2017-14025.
Tait Jr, R.G., Cushman, R.A., McNeel, A.K., Casas, E., Smith, T.P.L., Freetly, H.C., Bennett, G.L. 2018. µ-Calpain (CAPN1), calpastatin (CAST), and growth hormone receptor (GHR) genetic effects on Angus beef heifer performance traits and reproduction. Theriogenology. 113:1-7. https://doi.org/10.1016/j.theriogenology.2018.02.002.
Coleman, S.W., Chase, C.C., Phillips, W.A., Riley, D.G. 2018. Feed efficiency of tropically adapted cattle when fed in winter or spring in a temperate location. Journal of Animal Science. 96:2438–2452. https://doi.org/10.1093/jas/sky138.