Location: Livestock and Range Research Laboratory
2021 Annual Report
Accomplishments
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.
Review Publications
Geary, T.W., Waterman, R.C., Van Emon, M.L., Ratzburg, C.R., Lake, S., Eik, B.A., Armstrong, D.R., Zezeski, A.L., Heldt, J.S. 2021. Effect of supplemental trace minerals on standard and novel measure of bull fertility. Theriogenology. 172:307-314. https://doi.org/10.1016/j.theriogenology.2021.07.006.
Sumreddee, P., Hay, E.A., Toghiani, S., Roberts, A.J., Aggrey, S., Rekaya, R. 2021. Grid search approach to discriminate between old and recent inbreeding using phenotypic, pedigree and genomic information. Biomed Central (BMC) Genomics. 22.Article 538. https://doi.org/10.1186/s12864-021-07872-z.
Moorey, S.E., Monnig, J.M., Smith, M.F., Ortega, M., Green, J.A., Pohler, K.G., Bridges, G., Behura, S.K., Geary, T.W. 2021. Differential transcript profiles in cumulus-oocyte complexes originating from pre-ovulatory follicles of varied physiological maturity in beef cows. Genes. 12(6):893. https://doi.org/10.3390/genes12060893.
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.
