Location: Livestock and Range Research Laboratory
2024 Annual Report
Objectives
Objective 1. Determine the limiting nutrients for efficient growth of beef calves and reproduction in beef females grazing native forages at different stages of maturity.
Sub-objective 1A: Determine effects of autumn/winter utilization (i.e., dormant) rangeland forage utilization on heifer development, and subsequent reproductive performance.
Sub-objective 1B: Develop management strategies to improve rangeland cattle production and ecological stability through effective use of rangeland forage and supplementation of young cows.
Sub-objective 1C: Identify better strategies for extensive rangeland livestock operations to prepare for seasonal and/or extended droughts through strategic supplementation of mature cows that optimize milk constituents and improve calf gain.
Sub-objective 1D: Evaluation of livestock nutrition models for predicting weight gains/losses and body condition for livestock under supplemental and precision feeding.
Objective 2. Determine the limitations of efficient embryonic development involving successful placentation and implantation to mitigate embryonic losses that decrease reproductive efficiency in cattle.
Sub-objective 2A: Determine the physiological role of estradiol in endometrial function, conceptus growth, and gene expression that contribute to increased pregnancy success in cattle.
Sub-objective 2B: Determine specific nutritional impacts on ovum fertility and early embryonic development in beef heifers that contribute to pregnancy success.
Sub-objective 2C: Determine the effect of fertilization by suboptimal sperm on embryonic mortality in beef cattle.
Objective 3. Optimize selection and assign breeding to maintain genetic variation (limit inbreeding) in Line 1 Hereford population.
Sub-objective 3A: Utilize recombination rate to increase genetic variation and mitigate the accumulation of inbreeding.
Sub-objective 3B: Evaluate the effects of selection on runs of homozygosity on inbreeding depression and performance of Line 1 Hereford.
Objective 4. Determine G x E (genetic/genomic x environmental/management) interactions and the effect of heterozygosity on the composite trait of lifetime production efficiency in order to enable management practices that favor desired outcomes.
Sub-objective 4A: Determine effects of dry lot heifer development, and subsequent reproductive performance from dams developed on different nutritional planes and evaluate the genetic variation and the existence and extent of genotype by nutritional environment interaction in heifer development.
Sub-objective 4B: Determine differences in respiration gas fluxes throughout a production year from weaning to 3 years of age by cattle from dams developed on different planes of nutrition.
Sub-objective 4C: Determine effects of variation among adult cows that experienced in utero nutrient restriction on embryonic survival of genetically similar embryos and their performance as calves.
Approach
Feed consumption, genetic selection and reproductive efficiency, are primary determinants of beef production efficiency. Our overarching goal is to better define these variables and develop strategies and technologies to alleviate their limitations to beef production efficiency. 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 female retention rates. Our approach is, of necessity, multi-disciplinary, involving both basic and applied aspects of genetics, nutrition, and physiology in a semi-arid grazing production system. This plan brings to fruition ongoing research and establishes investigations of genetic by environmental interactions as well as nutritional and physiological mechanisms limiting reproductive success. Four distinct cattle populations (an intercross of Charolaise (25%), Red Angus (50%) and Tarentaise (25%) herd, Line 1 Hereford herd, Precision Livestock Hereford-Angus herd, and Physiology Hereford-Angus herd) will be used to facilitate assessment of genetic, strategic nutritional and physiological factors affecting productivity. Distinct nutritional environments differing in provision of strategic supplements to cattle grazing forage will be tested to challenge the nutrition-reproduction interface to reveal roles of genetic, physiological, and management factors influencing feed utilization and animal 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 that are most fit for rangeland environments. This research will result in the establishment of evidence-based selection, development and management protocols that provide producers options for addressing industry needs and dealing with climate and environmental variability.
Progress Report
Objective 1, Sub-objective 1A: Progress included collection of growth and reproductive success among heifers receiving strategic supplement of key amino acids during development. In addition, supplement intake is measured on an individual animal basis. Objective 1, Sub-objective 1B: Data has been collected from cows that were traditionally managed or whose performance was continually measured using precision measurement technologies for management decisions. GPS collars were deployed on a subset of the traditionally managed and precision managed herds and data were collected over 4 grazing periods during the summer and fall months. Pasture biomass data were collected before and after grazing period in the pastures used for the traditional and precision herds to monitor differential utilization. The pastures were also flown with an unmanned aerial vehicle (UAV) before and after grazing and used to estimate vegetation height and volume for use in models to predict pasture biomass. During spring and fall months, near infrared spectrometry readings were taken from quadrats in each of the pastures prior to clipping. After clipping, samples were dried and ground and sent to a forage lab for forage quality analysis. These data will subsequently be used in models to predict forage quality in the pasture using satellite and UAV data. Objective 1, Sub-objective 1C: Milk constituents, rumen microbiome, and calf growth data has been collected from cows receiving strategic supplementation before and after calving to determine the ability to improve performance by inclusion of calcium propionate and rumen protected fatty acids. Objective 1, Sub-objective 1D: Scripting and data aggregation schemes for climate and sensor data and database development for nutrition models are ongoing. Scripting was completing for analysis of GPS collar data to evaluate movement, grazing locations, and landscape use in traditional versus precision management grazed pastures. Scripting was also completed for downloading weather station data from onsite Montana Mesonet stations. Script development was initiated for automating nutritional model analysis based on inputs from sensors (weather and Smart-Scale measurements) and pasture forage quantity and quality information (derived from UAV and spectrometry measurements). Objective 2, Sub-objective 2A: Reproductive tissues and histomorphology have been collected, transcriptomics conducted, but data analyses has not been completed. Objective 2, Sub-objective 2B: Embryo and uterine secretions have been collected from heifers that received limiting or abundant energy and protein after fertilization to understand the effects of reduced nutrition on early embryo development and pregnancy success. When energy was limited in heifer diets, we observed altered conceptus gene expression and uterine metabolites available for embryo development. Analysis of transcriptomics information is ongoing. Objective 2, Sub-objective 2C: Additional laboratory analyses of bovine sperm biomarkers (especially negative biomarkers of fertility) was identified as a preliminary step to the planned field trial. Magnetic nanoparticles were coated with specific lectins that bound negative biomarkers of fertility and allowed removal of sub-fertile sperm from the ejaculate before freezing to enhance fertility of semen doses. In vitro analyses of these frozen-thawed semen doses allowed us to identify the best cocktail of nanoparticles for a field trial. The field trial is planned for Fall 2024 because of the decreased fertility associated with heat stress in dairy cattle. In a related project, specific biomarkers on frozen-thawed bull sperm associated with field fertility were identified in 2023 and continued work this year has evaluated these biomarkers in fresh compared to frozen-thawed semen to estimate the fertility potential of natural service field fertility of herd bulls. Another related project has begun that will compare the offspring parentage with in vitro semen biomarker evaluation of ejaculates from beef bulls used for natural service. Objective 3, Sub-objective 3A: A computer program has been developed to estimate the recombination rate of genes associated with important production traits in cattle. Preliminary results showed that Line 1 Hereford population has lower recombination rate than a composite population (CGC). Further, the average genetic recombination distance was 1.34 centimorgan per mega base for Line 1 and 1.36 centimorgan per mega base for Line 1. Several recombination hot spots were detected in Line 1 and the composite population, which potentially can be used in selection to inject genetic variation in inbred populations. Objective 4, Sub-objective 4A: Growth and performance data has not been collected from heifers as described within the research project because of strict culling that occurred within this herd of cattle to meet Montana Agriculture Experiment Station income requirements. There are no more cattle in this herd that will allow evaluation of heifers as proposed. In a related project involving these cattle, we have initiated evaluation of yearling heifer and bull fertility assessments related to in utero mineral treatment. Objective 4, Sub-objective 4B: Data related to respiration and production efficiency has been collected from heifers and two-year-olds with different epigenetic inputs. Objective 4, Sub-objective 4C: Embryos have been produced and transferred into cows from another herd because there are no longer any cows that had experienced in-utero nutrient restrictions available for study due to strict culling of older cows. In a related project involving these cattle, we have collected uterine microbiome samples for analyses and potential identification of the optimal uterine microbiome associated with pregnancy success.
Accomplishments
1. High fertility bulls have sperm that capacitate slower in vitro than low fertility bulls. Capacitation is an irreversible process that sperm must go through in the reproductive tract of females before they are capable of fertilization. ARS researchers at Miles City, Montana, have developed an in vitro assay that characterizes progression of capacitation among bovine sperm following freezing. Sperm from bulls that progressed more slowly through capacitation remained viable longer and resulted in greater pregnancy rates following timed artificial insemination. This in vitro assay might be able to predict field fertility of bulls and thus identify males that will yield greater pregnancy rates for livestock producers who utilize artificial insemination. A comparison of sperm cells from fresh ejaculates with samples following commercial freezing revealed similar responses. Thus, the addition of this in vitro capacitation assay to a standard breeding soundness evaluation conducted by veterinarians of herd bulls should allow identification of the most fertile bulls within a herd and allow producers using natural service to strategically use their more fertile bulls to improve productivity and profitability. Cows that conceive at their first opportunity during the breeding season would wean calves that are 40 to 50 pounds heavier and worth approximately $150 each more using current price estimates.
2. Genotype by environment genetic selection for cows better able to handle harsh winters. Cattle operations in the Northern Great Plains region of the United States endure extreme cold weather, requiring nutritional supplementation during winter to maintain body condition. In cow-calf operations, body condition scores (BCS) assessed at calving and breeding are linked to several economically significant health and fertility traits, making BCS maintenance crucial for both animal welfare and economic reasons. BCS has been found to have low to moderate heritability, with some cattle showing a better ability to withstand harsh cold with fewer resources. ARS researchers at Miles City, Montana, explored genotype by environment interactions at pre-calving and pre-breeding under three winter supplementation strategies. A genotype by environment interaction for pre-calving BCS in one supplementation group (self-fed access to high protein supplement during winter) indicates the potential for selection of animals with increased resilience under cold weather conditions and high protein supplementation to maintain BCS. Producers could use genetic selection to identify cows better adapted to utilize available rangeland resources with lower supplemental costs and increase herd profitability.
3. Genetic selection potential for healthier beef production. Carcass traits are considered economically important in the beef cattle industry. ARS researchers from Miles City, Montana, collaborated with researchers from China to investigate the fat composition of muscle in Simmental cattle to better understand meat quality. Using genome analysis tools, we explored the genetic factors influencing different fatty acids associated with healthier meat production. A specific marker was identified that may allow genetic selection for improved (healthier) meat quality in beef production. Additional research is warranted to determine the value of genetic selection for this marker before a beneficial effect is realized by producers and consumers of beef.
Review Publications
Santana, B., Riser, M., Hay, E.A., Fragomeni, B. 2023. Alternative SNP weighting for multi-step and single-step genomic BLUP in the presence of causative variants. Journal of Animal Breeding and Genetics. 140(6):679-694. https://doi.org/10.1111/jbg.12817.
Wang, Z., Ma, H., Li, H., Xu, L., Zhu, B., Hay, E.A., Xu, L., Li, J., Li, H. 2023. Multi-trait predictions using GBLUP and Bayesian mixture prior model in beef cattle. Animal Research and One Health. 1(1):17-29. https://doi.org/10.1002/aro2.13.
Ling, A.S., Hay, E.A. 2024. The effects of genotype-by-environment interactions on body condition score across three winter supplemental feed environments in a composite beef cattle breed in Montana. Journal of Animal Science. 8. Article txae024. https://doi.org/10.1093/tas/txae024.