Location: Livestock Bio-Systems
2023 Annual Report
Objectives
Objective 1: Evaluate and improve genetic resources across diverse production systems and environments.
Sub-objective 1.A: Characterize genetics that are fit to different lambing production systems and mating seasons. There are two experimental populations that contribute to this sub-objective, the Composite IV maternal line and the purebred Polypay flock.
Sub-objective 1.B: Measuring genetic variation interactions with different production environments and management systems. This sub-objective will be addressed with two experiments. One experiment that estimates interactions at the intra-locus level using genetic variation for a gene that codes for the bone morphogenic protein receptor 1 beta (BMPR-1B) and one experiment that documents interactions at the whole animal performance level across different locations and production systems to estimate levels of GEM interactions.
Objective 2: Develop complexes of novel traits to serve as indicator traits associated with improved production efficiencies.
Sub-objective 2.A: Characterize behavior traits in rams, ewes, and lambs.
Sub-objective 2.B: Characterize feed intake, carcass, health, and longevity traits of ewes and lambs.
Approach
Production inefficiencies threaten the ability of U.S. sheep producers to remain competitive with other domestic meat animal species and foreign sheep industries. The American Lamb Industry Roadmap Project identified several goals to overcome these obstacles. High priority was given to increased producer use of quantitative genetic selection tools which highlights the need for continued development of genetic technologies and adoption by the U.S. sheep industry. To support this industry goal, this project plan focuses on evaluating novel traits associated with animal health, behavior, and performance in multiple populations reared in diverse production environments and management systems. Specifically, we will estimate genetic and non-genetic covariation of economically important yet difficult to measure traits alongside more easily measured indicator traits already in use by industry breeders. Trait complexes evaluated will include susceptibility to common periparturient diseases and longevity of ewes; lamb survival, growth, feed intake, and carcass characteristics; ewe reproductive performance and maternal behaviors across mating seasons and lambing environments; and ram behavior and breeding capacity. Results from this work will serve as the foundation for developing new selection criteria for use in national breeding programs. Concurrent genotyping efforts will direct the identification of genomic regions associated with phenotypic variation and advancement of genomic-enhanced selection decisions. A key component of this effort will be to strengthen genetic relationships between flocks across USDA ARS locations at the U.S. Sheep Experiment Station and Dale Bumpers Small Farms Research Center which will, in turn, enable genetic x environment x management systems interactions to be evaluated for the first time in U.S. sheep populations. Germplasm from industry flocks will be routinely sampled thereby accelerating the dissemination of experimental findings. Results will improve our understanding of genetic and non-genetic factors which impact sheep well-being and productivity and provide sheep industry stakeholders with novel genetic selection tools for flock improvement.
Progress Report
Sub-Objective 1A: ARS researchers at Clay Center, Nebraska, have collected fertility and productivity data for the third year within the Composite IV population on pasture lambing ewes (270 ewes/year) and more intensive data collected on 120 ewes per year in a barn setting where lambing behavior traits are monitored by digital cameras. One year of fertility and reproductive efficiency data has been collected in spring and fall annual lambing Polypay ewes (approximately 600 ewes). A portion of ewes had DNA submitted for genotyping, which will further enhance future efforts to identify genetic variation associated with fertility. Data collection from this experiment will continue through FY2024 and beyond.
Sub-Objective 1B: ARS researchers at Clay Center, Nebraska, Booneville, Arkansas, and Dubois, Idaho, coordinated germplasm exchange among locations and collected data associated with health and productivity, which is necessary for future efforts to explain components of observed variation associated with environment and management systems that could interact with genetics. Data collection from this experiment will continue through FY2024 and beyond. ARS researchers at Clay Center, Nebraska, have screened the Romanov population and identified a heterozygous ram that has now produced progeny in the flock the last two years. Screening additional animals continues as we build the population for evaluation.
Sub-Objective 2A: ARS researchers at Clay Center, Nebraska, completed a three-year experiment to quantify components of ram mating behavior. Preliminary analyses have been presented at two scientific conferences. Annotation has begun on behavior data captured from video. Annotation of images collected for maternal and lamb behavior components has begun from three years of lambing data collected.
Sub-Objective 2B: ARS researchers at Clay Center, Nebraska, have collected data from two separate multi-year experiments associated with ewe longevity and lamb feed efficiency/carcass characteristics. Preliminary results from carcass evaluations have been presented at two scientific conferences. Graduate students from the University of Nebraska-Lincoln and Purdue University have begun preliminary analyses on factors associated with ewe longevity. Data collection from both experiments will continue through FY2024 and beyond.
Accomplishments
1. Comparison of three maternal composite sheep breeds managed under pasture lambing. Comparison of three maternal composite sheep breeds managed under pasture lambing. Extensively managed sheep operations primarily in the western states are the predominant production system where approximately 60% of lambs are born outside with little intervention. Relatively low numbers of lambs born per ewe by traditional sheep breeds in these low-input systems are a barrier to economically sustainable production. ARS researchers at Clay Center, Nebraska, compared three maternal composite breeds of sheep under a low-input pasture lambing production system over 4 years. The Composite-IV, a sheep breed developed at Clay Center, Nebraska, and selected for enhanced reproductive efficiency in a lower-input system, produced 44% more lambs than the other two breeds and marketed 20% more lamb weight than Polypay and 40% more than Katahdin ewes. At a value of $2 per pound of lamb weight marketed each individual Composite-IV ewe generated $156 more than each Polypay ewe and $270 more than each Katahdin ewe during the 4 years. The large differences in maternal ability between these breeds can now be used by commercial sheep producers to increase lamb production in low input systems.
Review Publications
Freking, B.A., Murphy, T.W., Chitko-McKown, C.G., Workman, A.M., Heaton, M.P. 2022. Impact of four ovine TMEM154 haplotypes on ewes during multiyear lentivirus exposure. International Journal of Molecular Sciences. 23(23). Article 14966. https://doi.org/10.3390/ijms232314966.
Murphy, T.W., Freking, B.A., Bennett, G.L. 2022. Comparison of three maternal composite sheep breeds managed under pasture lambing and purebred or terminal mating systems: Ewe body weight, reproductive efficiency, and longevity. Journal of Animal Science. 101. Article skac418. https://doi.org/10.1093/jas/skac418.
Florez, J.M., Martins, K., Solin, S., Bostrom, J.R., Rodriguez-Villamil, P., Ongaratto, F., Larson, S.A., Ganbaatar, U., Coutts, A.W., Kern, D., Murphy, T.W., Kim, E., Carlson, D.F., Huisman, A., Sonstegard, T.S., Lents, C.A. 2023. CRISPR/Cas9-editing of KISS1 to generate pigs with hypogonadotropic hypogonadism as a castration free trait. Frontiers in Genetics. 13. Article 1078991. https://doi.org/10.3389/fgene.2022.1078991.
