To remain globally competitive, the U.S. sheep industry must increase the volume and quality of marketable products. Yet, domestically, U.S. sheep producers must also achieve ecologically positive production systems to remain viable. Although consumer demand for U.S. sheep meat and wool products is robust, changing societal demands for public rangeland use, lagging acceptance of genetic tools, and production inefficiencies hamper the ability of the U.S. sheep industry to generate quality meat and wool at viable profit margins. Fashioning integrated sheep genetic resources to enhance rangeland ecological functions, creating national sheep reference flocks, developing solutions to increase lamb survivability, and extending ewe longevity would foster robustness and competitiveness of the U.S. sheep industry and the sustainability of rural livelihoods. To this end, our aim is to develop ecologically oriented sheep genetic resources and production tools to increase lifetime production efficiency and ecological utility of sheep originating from rangeland production systems. Our approach involves integrated efforts with universities and other Agricultural Research Service units to advance the discovery of unique traits and genetic markers associated with herbivory preferences of grazing sheep, facilitate robust genetic x environment x management evaluations and discovery of novel production efficiency traits, and develop solutions to mitigate anti-productive effects of sheep diseases and reduce the sheep industry’s use of antibiotics. Accordingly, the project plan objectives and subobjectives are: Objective 1: Develop ecologically-oriented sheep genetic resources applicable towards increasing lifetime production efficiency and grazing utility of sheep originating from extensive rangeland systems. Subobjective 1.A: In sheep, quantify the association between taste sensitivity towards bitter flavor and herbivory of browse species. Subobjective 1.B: In sheep, identify genetic markers/candidate genes that are associated with taste sensitivity towards bitter flavor. Objective 2: Develop non-antibiotic solutions for increasing sheep longevity in the production system. Subobjective 2.A: Determine the utility of chlorate salts to mitigate anti-productive effects of sub-clinical mastitis in early and near-peak lactation ewes on annual weight of lamb weaned. Accomplishment of these objectives will result in sheep genetic resources applicable for enhancing and conserving ecosystems, solutions for increasing ewe production efficiency, and non-antibiotic alternatives to increase ewe longevity and lamb survival. Stakeholders include those focused on meat and wool production and marketing, genetic flock resources, land management, habitat and wildlife conservation, and targeted grazing.
For Objective 1, we will develop of series of tests to identify sheep with low to high taste sensitivity towards bittering compounds placed in the feed, determine the herbivory preferences of sheep based on sensitivity towards bitter flavor, and further validate use of genetic markers to identify sheep with specific taste sensitivities and herbivory preferences. Experimental goals specific to Objective 1 are: 1) Develop a feed-based, bitter-taste sensitivity classification method that generates precise classification results in agreement with Hensley et al. (2019); 2) Develop a high-throughput, feed-based, bitter-taste sensitivity classification method where multiple sheep in group-fed environments can be simultaneously classified; 3) Determine if bitter-taste sensitivity can be used as an accurate predictor of sheep herbivory of shrubs in an actual grazing application; and 4) Identify genetic markers/candidate genes that are useful for identifying and predicting herbivory of sheep. For Objective 2, we will extend previous efforts in evaluating the effect of adding sodium chlorate to the drinking water of periparturient ewes to reduce diseases associated with pathogenic Enterobacteria. The experimental hypothesis (alternative) specific to Objective 2 is: Ewe consumption of sodium chlorate (via drinking water) at early and near-peak lactation reduces occurrence of Escherichia coli-induced subclinical mastitis in sheep and, thus, mitigates anti-productive effects of mastitis. Specific focus will be placed on evaluating performance and productivity of ewes and lambs from an environment where measures are taken to reduce the likelihood of disease.
This report documents progress for project 2056-31610-007-000D, Agroecological Approach to Enhance U.S. Sheep Industry Viability and Rangeland Ecosystem Conservation, which started June 2022 and continues research from expired project 2056-31610-006-000D, Enhancing Sheep Enterprises and Developing Rangeland Management Strategies to Improve Rangeland Health and Conserve Ecology. For additional information, see the expired project.