1a. Objectives (from AD-416):
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.
1b. Approach (from AD-416):
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.
3. Progress Report:
This new project is a continuation of research from expired projects 2056-31610-005-00D and 2056-31000-011-00D. Significant progress was made on Objectives 1 and 2. In support of Sub-objective 1.A, a new sheep terminal-sire composite breed (TSC) was developed during the previous National Program (NP) 101 project plan cycle. The first year’s comparison of the TSC breed to the Suffolk (industry standard breed) and Siremax (new industry breed) terminal-sire breeds was successfully initiated by mating Suffolk, Siremax, and TSC breed sires (rams) to range-type ewes. Under Sub-objective 1.B, intensive genetic analyses and improvement of Targhee and Rambouillet breeds was conducted during project plan cycles dating back several decades. Datasets resulting from former project plans were successfully extracted from the location’s genetic database and uploaded into the National Sheep Improvement Program (NSIP) database. Furthermore, NSIP-registered Targhee, Rambouillet, and Merino sheep breed sires were purchased from the industry and mated to the location’s nucleus Targhee and Rambouillet ewe flocks to create NSIP industry-linked flocks. Related to Sub-objective 1.C, a safe and efficacious dose of sodium chlorate, an antibiotic-alternative compound to be placed in the drinking water of birthing ewes, was established in the previous NP101 project plan cycle. In a commercial-style production system, first-birth ewes were successfully treated with the antibiotic-alternative compound, and post-treatment performance and health data were collected from treated ewes and their offspring. For Sub-objective 2.A, a prescribed burn was conducted during the previous NP215 project plan cycle. The first year’s vegetation and sage grouse habitat assessments were successfully conducted on the burned sites. Based on the assessments and using formerly developed post-fire shrub-recovery models, grazing plans were initiated.
1. Aiming for responsible lamb production. To increase the annual U.S. lamb crop, some industry leaders are suggesting that ewes should be rearing triplet litters. However, is it feasible for ewes to rear triplet litters considering the harsh environments of the U.S. West mountainous regions, where greater than 40% of the U.S. sheep inventory exists? ARS researchers near Dubois, Idaho, in cooperation with Virginia Tech University in Blacksburg, Virginia used sheep composite breeds produced at the U.S. Sheep Experiment Station and U.S. Meat Animal Research Center to answer this question. Scientists established that a flock average litter size of 2.2 lambs per ewe each year is optimal. Furthermore, average litter sizes greater than 2.2 are of minimal value given the high death rate found with ewes rearing triplet litters. Results are being used by the U.S. sheep industry to guide producers in responsibly selecting breeds and genetics that will improve lambing rates towards manageable and profitable levels.
Lewis, G.S., Wang, S., Taylor, J.B. 2017. Responses of pregnant ewes and young lambs to ovalbumin immunization, antiovalbumin antibody transfer to lambs, and temporal changes in antiovalbumin antibody. Journal of Animal Science. 1:585-591.
Adler, P.B., Kleinhesselink, A., Hooker, G., Taylor, J.B., Ellner, S.P. 2018. Weak interspecific interactions in a sagebrush steppe? Conflicting evidence from observations and experiments. Journal of Ecology. 99:1621-1632.
Taylor, J.B. 2016. Breeding ewe lambs at 7 to 9 months of age. In: Redden, R., Morrical, D., editors. Best Practices to Increase Your Lamb Crop. Red Owl, SD: Demeter Communications. p. 9-14.
Panter, K.E., Taylor, J.B., Lee, S.T., Strong, N.K., Wierenga, T.L., Cook, D., Welsh, S.L. 2017. Lupine poisoning in sheep on the USDA-ARS U.S. Sheep Experiment Station (USSES), Dubois, Idaho. International Journal of Poisonous Plant Research. 4:79-87.