Location: Livestock and Range Research Laboratory2021 Annual Report
Objective 1: Evaluate effects of heifer development and winter supplementation protocols that differ in level and type of harvested feed inputs on the sustainability of beef production systems, including annual reproductive success, lifetime productivity, and progeny performance. Component 1: Problem Statement 1A, 1B Objective 2: Establish postweaning heifer development protocols that provide opportunities for improved fertility and differential forage utilization. Component 1: Problem Statement 1A, 1B Objective 3: Integration of phenomics and genomics data to dissect the genetic basis of reproductive and growth traits in beef cattle. Component 1: Problem Statement 1A, 1B Component 2: Problem Statement 2A, 2B, 2D Objective 4: Study the effect of environment, management and genetic interaction on range beef cattle production. Component 1: Problem Statement 1A, 1B Component 2: Problem Statement 2B, 2D We have proposed a series of experiments that will contribute to the alleviation of rate limiting factors that compromise beef production efficiency by: 1) Collectively increasing knowledge of the phenotypic and genetic interplay between nutrition and lifetime reproductive efficiency (Objectives 1, 2, 3 and 4) thus facilitating the economic optimization of feed level and identification of germplasm that is of less risk of reproductive failure when feed level is reduced; 2) Developing strategies that will provide producers management approaches to better utilize forage and better cope with yearly environmental variation (Objective 1, 2, and 4); 3) Further identifying phenotypic and genomic factors controlling fertility in bulls and establishment and maintenance of pregnancy in females thus leading to targets for managerial interventions that increase pregnancy rate, decrease replacement rate and reduce cost associated with producing replacement females (Objective 1, 3, and 4); 4) Prioritizing weighting of phenotypic and genotypic traits influencing production at the time selection decisions occur (typically at approximately one year of age) targeting lifetime performance (Objectives 1, 2, 3, and 4) thus facilitating selection of breeding stock for efficient low-cost production. Work needed to accomplish our objectives is multi-disciplinary and contributions from more than one scientist are expected in order to bring each objective to fruition.
Feed consumption and replacement of cows, culled for reproductive failure, are two primary determinants of beef production efficiency. Our overarching goal is to develop strategies and technologies to alleviate these limitations. Sufficient nutrient intake resulting in adequate body energy stores are believed essential for reproduction. Thus, producers are challenged to match nutritional environment, which is subject to seasonal and annual variation, and various genotypes to obtain sustainable reproduction and retention rates. Our approach is, of necessity, long-term and multi-disciplinary, involving both basic and applied aspects of genetics, nutrition, and physiology in a semi-arid grazing production system. This proposal brings to fruition ongoing research and establishes investigations of genetic by environmental interactions and physiological mechanisms limiting reproductive success. Four distinct cattle populations (an intercross of Charolaise (25%), Red Angus (50%) and Tarentaise (25%), Line 1 Hereford, purebred Angus, and Hereford-Angus herd) will be used to facilitate assessment of genetic factors affecting fitness (hybrid vigor). Distinct nutritional environments differing in provision of harvested or grazed forage will be tested to challenge the nutrition-reproduction interface to reveal roles of genetic, physiological, and management factors influencing feed utilization and lifetime productivity. Identification of genetic, nutritional, and physiological mechanisms that limit or contribute to beef production efficiency will facilitate early in life selection and management of replacement animals most fit for particular production environments. This research will result in the establishment of evidence based beef female development and management protocols that provide producers options for dealing with annual environmental variations.
Objective 1, Sub-objective 1A: Progress on our project included continuation of female retention (pregnancy success) within the Red Angus/Charolais/Tarentaise-composite cow herd and offspring performance to one year of age. Calf growth and reproductive performance data have been analyzed. Objective 2, Sub-objective 2A: Forage utilization of heifers during development was recorded for heifers developed in the feedlot and estimated for heifers developed on range. Objective 2, Sub-objective 2B: Post-weaning development of these heifers did not influence herd retention but did influence grazing behavior upon introduction to spring/summer pastures. Objective 2, Sub-objective 2C: No additional data are being collected. Research compared precision of two methods of estimating activity of rangeland heifers monitored with collars equipped with GPS and motion sensors: One method used movement velocity thresholds from GPS data and the second method was based on distance thresholds from GPS data and 2-axis accelerometer data. Both methods yielded similar estimates for time spent resting and grazing. Differences between the two methods were found in estimated time spent traveling. Both methods presented an acceptable degree of concordance. The GPS method appeared to be a reliable means of estimating cattle activities within certain limits. GPS data revealed that heifers developed in the feedlot traveled farther and covered larger areas of the pasture during the first few days of spring grazing than heifers developed on range and provided a protein supplement. Objective 2, Sub-objective 2D: Post-weaning performance data collection of calves has continued to allow comparison of developmental nutrition management on progeny performance. Objective 3, Sub-objective 3A: A genome-wide association study of longevity was conducted, and results revealed several quantitative trait loci associated with longevity. Moreover, a study on genomic prediction of fertility traits was conducted and results indicated that inclusion of genomic information increased the genetic prediction of pregnancy status by 26 to 29%. Manuscripts evaluating change in heterozygosity and genetic composition in a composite beef cattle population and evaluation of early fertility traits are in preparation. Summarization of feed intake data is underway. Objective 3, Sub-objective 3B: Bull fertility phenotypes and semen were collected in 2018 and 2019 from yearling bulls within the Line 1 Hereford-Angus heterosis project and evaluated using standard and 4 novel flow-cytometry measures of fertility. Samples were then frozen and further evaluations post-thaw have been conducted. We have not yet completed analyses of the post-thaw evaluation of these semen samples. Additional studies on bull fertility were conducted in which yearling bulls were fed a high distillers grain (feed high in sulfur) or sulfate supplementation. Bulls fed diets high in distillers grain produced sperm with decreased ability for prolonged motility/lifespan than control bulls and bulls fed a diet high in sulfur. An additional fertility evaluation has been performed on frozen/thawed semen of bulls with known high and low field fertility. Preliminary analyses revealed that some of our measures may be predictive of field fertility but will require sampling a larger population. More detailed evaluation of these sperm biomarkers may provide enhanced scrutiny of bull fertility and improve developmental management for bull fertility. Objective 3, Sub-objective 3C: As part of the Grand Challenge collaboration with ARS researchers in Clay Center, Nebraska, and Fort Collins, Colorado, growth and carcass data were collected for calves finished in 2020 and is ongoing for calves being finished in 2021. Objective 4, Sub-objective 4A: Growth and reproduction data on heterosis animals are still being collected. Analysis and characterization of inbreeding in Line 1 Hereford using genomic data has been completed. Objective 4, Sub-objective 4B: Pregnancy success is greater and embryonic mortality is less among cows that are induced to ovulate a large (physiologically mature) follicle compared to a small (physiologically less mature) follicle. Research indicates that physiologically immature oocytes lack the transcripts, and thus enzymes available, to provide adequate energy to support embryo development and pregnancy success. Objective 4, Sub-objective 4C: Cows that ovulate a larger follicle also experience greater circulating concentrations of preovulatory estradiol and progesterone during early pregnancy. Inadequate preovulatory estradiol and inadequate progesterone during early pregnancy both decrease embryo survival & pregnancy maintenance. Mechanistic studies were begun by ARS researchers in collaboration with Texas A&M University and University of Missouri scientists to determine how preovulatory estradiol improves embryo survival.
1. Crossbreeding: a different perspective. Crossbreeding is a common management practice used by livestock producers in the U.S. and around the world. The main benefits of crossbreeding are heterosis and breed complementarity. ARS scientists at Miles City, Montana, have conducted genomic analysis of heterosis in an Angus x Line 1 Hereford population to evaluate its effects on growth traits using single nucleotide polymorphism (SNP) data and detection of regions on the genome associated with heterosis. Significant effects of genomic heterozygosity on growth traits were observed. These effects included a 0.76 kg decrease in birth weight, a 4.67 kg increase in weaning weight, and a 42.39 kg increase in yearling weight. Genome wide association study revealed several SNP markers with significant heterotic effects associated with birth weight, weaning weight and yearling weight. These SNP markers were located on chromosomes 1, 2, 14, 19, 13 and 12. Genes in these regions are involved in growth and other important physiological mechanisms. Similar results could be used by producers to select specific dams and sires for mating to optimize crossbreeding.
2. Classifying inbreeding. Several methods have been proposed to classify inbreeding using pedigree and genomic data. Unfortunately, these methods are largely based on heuristic criteria such as the number of generations from a common ancestor, or length of runs of homozygosity (ROH) segments. To address these deficiencies, ARS scientists at Miles City, Montana, developed a method to classify pedigree and genomic inbreeding into recent and ancient classes. The proposed method was tested using the Line 1 Hereford population. Four growth traits (birth weight, weaning weight, yearling weight, and average daily gain) were used to assess recent and ancient inbreeding. Thresholds to classify inbreeding into recent and ancient classes were trait-specific and varied across traits and sources of information. Using pedigree information, inbreeding generated in the last 10 to 11 generations was considered as recent. When genomic information (ROH) was used, thresholds ranged between four to seven generations, indicating that ROH segments allow us to characterize the negative effects of inbreeding in shorter periods of time. However, the discrimination between new and old inbreeding was less robust when ROH segments were used compared to using pedigree information. Using several model comparison criteria, the proposed approach was generally better than existing methods. Recent inbreeding proved to be more harmful across all traits analyzed. However, both new and old inbreeding were found to be associated with decreased yearling weight and average daily gain.
3. Uterine signaling for improved fertility in cattle. Pregnancy loss is common in cattle and costs the beef and dairy industries more than $90 M annually. Identifying the causes of embryo loss is necessary for improving productivity. The size of the follicle that releases an oocyte (egg) during ovulation affects pregnancy success. Pregnancy rates are decreased when a small follicle ovulates in heifers or is induced to ovulate in cows. These decreased pregnancy rates are a function of increased embryo mortality. Smaller follicles produce less estradiol, and luteal tissue derived from follicle cells produce less progesterone during early pregnancy. Estradiol and progesterone are known to prepare the uterus for pregnancy. However, because both hormones are produced from the same ovarian cells, the independent effects of greater estradiol before and progesterone after ovulation are confounded. ARS researchers at Miles City, Montana, collaborated with colleagues at the University of Missouri and South Dakota State University to investigate the effects of estradiol before ovulation and progesterone after ovulation. Cows were grouped by high or low estradiol and high or low progesterone into 4 treatment groups. Cows in all 4 treatments received embryos to study embryo survival. Higher estradiol levels before ovulation improved the survival of embryos. Higher progesterone levels after ovulation only improved embryo survival in cows with low estradiol. Thus, when producers use techniques like artificial insemination or embryo transfer to improve genetics, the method used to prepare cows for pregnancy is critical. Treatments that increase estradiol levels before ovulation will improve pregnancy success among more cows than those that increase progesterone after ovulation. Treatments that increase both would have the greatest effect on the uterus and yield greater pregnancy success.
4. Oocyte maturity limitation affecting fertility in cattle. Pregnancy loss is common in cattle and costs the beef and dairy industries more than $90 M annually. Fertilization rates are high (~90%) in cattle but approximately 30% of beef and 50% of dairy cow embryos die. Most embryonic mortality occurs within the first 28 days after fertilization. Both oocyte quality and uterine support play major roles in embryo development and survival. ARS researchers at Miles City, Montana, collaborated with University of Missouri and Tennessee scientists to understand how oocyte maturity might affect pregnancy success in cows. An individual oocyte (egg) ovulates approximately 24 hours after the onset of estrus or induced ovulation in cattle. This oocyte must contain all the gene transcripts required for an embryo to grow and survive for approximately three days until the embryo genome takes over. Oocytes were recovered from follicles six hours before anticipated ovulation that differed in size (small versus large) or physiological maturity (cows that expressed estrus or no estrus). Cumulus cells which serve as nurse cells for the developing oocyte were also recovered. Induced ovulation of larger (more mature) follicles yields oocytes with greater pregnancy rates than oocytes from small follicles. Gene transcripts differed greatly between oocytes and cumulus cells based on maturity level. Cumulus cells and oocytes from less mature follicles had decreased capacity for energy production. This likely contributes to the decreased competency of oocytes from small follicles. Methods to increase follicle size before ovulation during fixed time insemination or oocyte collection for in vitro techniques are practical applications to improve pregnancy success.
5. Mineral supplementation and bull fertility. After the breeding season, bulls often receive the poorest pasture and poorest feed available on a farm or ranch. This may be justified because bulls would have lower nutritional requirements than other classes of cattle. Mineral requirements of most classes of livestock are known, but no mineral requirements have been defined for bulls. Minerals, specifically zinc and copper, are involved in sperm development, maturation, and function and have been used to improve fertility in some species. ARS researchers from Miles City, Montana, and scientists from Montana State University evaluated common and new measures of fertility in bulls fed zinc and copper. Mature bulls were fed either no mineral or mineral that differed in availability for 71 days. Yearling bulls were provided no mineral, zinc, copper, or zinc and copper for 84 days. Mature bulls fed no mineral, or the less available mineral were copper deficient, but there were no effects on fertility. Fertility measures improved on yearling bulls from the beginning to the end of the study, but mineral had no effect on fertility measures. Bulls must have very low requirements for zinc and copper and/or very efficient mechanisms for recycling and conserving zinc and copper.
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Waterman, R.C., Vermeire, L.T. 2021. Annual bromes decrease with increasing fall defoliation intensity. Global Ecology and Conservation. 28. Article e01652. https://doi.org/10.1016/j.gecco.2021.e01652.
Waterman, R.C., Vermeire, L.T., Reinhart, K.O., Rinella, M.J. 2021. Influence of grazing season, residual herbage, and precipitation on rumen extrusa diet quality. Rangeland Ecology and Management. 78:117-126. https://doi.org/10.1016/j.rama.2021.06.004.
Sumreddee, P., Toghiani, S., Hay, E.A., Roberts, A.J., Aggrey, S., Rekaya, R. 2020. Runs of homozygosity and analysis of inbreeding depression. Journal of Animal Science. 98(12):1-11. https://doi.org/10.1093/jas/skaa361.
Ciernia, L.A., Perry, G.A., Smith, M.F., Rich, J.J., Northrop, E.J., Perkins, S.D., Green, J.A., Zezeski, A.L., Geary, T.W. 2021. Effect of estradiol preceding and progesterone subsequent to ovulation on proportion of postpartum beef cows pregnant. Animal Reproduction Science. 227. Article 106723. https://doi.org/10.1016/j.anireprosci.2021.106723.