Project Number: 2056-31610-006-000-D
Project Type: In-House Appropriated
Start Date: Aug 14, 2017
End Date: Aug 13, 2022
The ARS Grand Challenge calls for a transformation in U.S. agriculture that results in 20% more quality products, with a 20% reduction in environmental resource impacts by 2025. At the Range Sheep Production Efficiency Research Unit (RSPER), also known as the U.S. Sheep Experiment Station, our objectives are based on the premise that the rangeland ecosystem is the environmental resource base and that stakeholder products are quality meat and fiber from sheep and multi-use resilient rangelands. Accordingly, objectives were developed to reflect that food-animal production and rangeland management must be compatible and complementary. Research objectives are long-term, leveraging former and historic experimental accomplishments to achieve goals of increasing production efficiency, while simultaneously generating ecological benefits. RSPER’s extensive and historic databases of sheep production and genetic endpoints, rangeland vegetation variables, climate measures, and wildlife records were critical in developing project plan objectives. Consistent with the Grand Challenge, our purpose is to equip rangeland sheep producers with research-based tools, solutions, and data necessary to increase the annual weight of quality lamb and wool from ewes at a positive return to the rangeland resource base. Specifically, during the next five years we will focus on: Objective 1: Increase lifetime reproduction efficiency, net production yield, and product quality of range-type wool flocks. Subobjective 1.A (experimental): Evaluate Suffolk, Siremax, and RSPER terminal-composite (TSC) for ability to increase quantity and value of lamb. Subobjective 1.B (initiative): Establish genetic linkages between experimental and industry flocks to support industry-wide genetic evaluations and development of comprehensive breeding objectives. Subobjective 1.C (experimental): Determine the utility of chlorate salts to mitigate production losses due to postpartum diseases. Objective 2: Estimate ecological value of rangeland management practices in accomplishing Objective 1. Subobjective 2.A (experimental): Determine the sheep-production and ecological value of using sheep grazing to improve sage grouse-nesting habitat in recently-burned mountain big sagebrush steppe. Objectives are presented as either “experimental” or “initiative.” Experimental objectives are hypothesis driven and accomplished by controlled experimental designs with treatment replication. Initiative objectives are goal driven and aimed at coordinating large datasets or creating opportunities that can be used by others immediately or in the future for discovery-, development-, or solution-oriented research.
The hypothesis of Obj. 1.A is: “The main factors influencing the value of individual lambs and the lamb-crop as a whole, such as lamb survival, growth rate, and carcass yield and quality, differ between lambs sired by the new Siremax composite and Terminal Sire Composite (TSC) breeds and the industry standard Suffolk breed.” In-house TSC rams and a nation-wide sampling of Suffolk and Siremax rams will be mated to wool-type ewes. Offspring will be reared in a rangeland production system, subsequently weaned, finished, and slaughtered. Lamb pre-weaning and finishing health and performance and carcass yield and quality will be measured, and data will be analyzed to determine sire breeds and sires that excel at the traits of interest. The goals of Obj. 1.B are to: “Migrate Range Sheep Production Efficiency Research Unit (RSPER) genetics database to the National Sheep Improvement Program (NSIP)” and “Create NSIP-relevant linkages of RSPER flocks to the U.S. sheep industry.” The RSPER genetics database for Rambouillet, Targhee, Polypay, and Suffolk breeds will be uploaded to the Nat'l Sheep Improvement Prog. (NSIP) database. In order to develop NSIP-relevant linkages, a nation-wide sampling of NSIP Rambouillet, Targhee, Merino, and Merino-composite rams across the nation will be purchased from the industry and mated to RSPER Rambouillet and Targhee ewes. Ewe offspring will be retained in the RSPER flock and lifetime production data will be uploaded to NSIP. The hypothesis of Obj. 1.C is: “Ewe consumption of chlorate salts during early lactation will alter incidences of lamb diarrhea and ewe mastitis and weight-of-lamb weaned from ewes.” Ewes, beginning as yearlings, will be treated with chlorate or no chlorate (control) via drinking water for 4 days immediately after lambing. This treatment regimen will be repeated annually. Four-year cumulative ewe health and production performance will be calculated based on annual health measurements of lamb diarrhea and ewe mastitis morbidity, total count lambs birthed and weaned, and total weight of lambs birthed and weaned. Data will be analyzed to determine efficacy of chlorate to reduce mastitis and diarrhea morbidity in shed-lambing systems and improve lifetime production of range-type ewes. The hypothesis of Obj. 2.A is: “Post-burn recovery rate of sagebrush canopy cover, a critical factor of sage grouse-nesting habitat, and ewe productivity will be altered based on the season and intensity of grazing management.” Sixteen recently-burned pastures that are in the exponential shrub recovery phase will be assigned to 1 of 4 annual sheep grazing treatments of no spring or fall grazing, moderate spring and fall grazing, light spring and moderate fall grazing, and no spring and heavy fall grazing. The responses of plant community, dominant shrubs, forage production, and sage grouse-nesting habitat suitability will be measured annually. Sheep production will be measured, and dietary selection of sagebrush will be determined by near-infrared spectroscopy of ewe fecal samples. Data will be analyzed to determine the effect of timing of sheep grazing on sage grouse habitat sustainability and sheep production.