Location: Range Sheep Production Efficiency Research
2020 Annual Report
Objectives
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.
Approach
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.
Progress Report
Substantial progress was made towards completing Objective 1, increasing lifetime reproduction efficiency, net production yield, and product quality of range-type, wool sheep. For Sub-objective 1A, industry and ARS meat-type rams (male sheep) were purchased and cross-mated to wool-type ewes (female sheep). Rams were from Suffolk and Siremax breeds, and a new breed, developed by ARS researchers at Dubois, Idaho. The new breed was developed to confer greater survivability, health, and carcass quality to offspring that were produced in a U.S. West, extensive, range-type system. The crossbred offspring from these matings were evaluated for survival, health, growth, efficiency, and carcass quality and value.
For Sub-objective 1B, performance data from the Polypay sheep breed were successfully uploaded into the National Sheep Improvement Program (NSIP) genetics database. The NSIP is a program that U.S. sheep producers use to evaluate and identify superior genetics within their flocks and subsequently initiate breeding strategies that improve the genetics of their flock and flocks nationwide. For NSIP to be of the greatest benefit, genetic linkages (kinship) must be established across all U.S. flocks within each breed. ARS researchers at Dubois, Idaho, purchased industry rams, registered in NSIP, and mated these to ARS ewes. Progeny (offspring lambs) data from the matings were uploaded into NSIP, resulting in extensive enhancement of the industry genetic linkages within NSIP for the Polypay sheep breed. Currently progress is being made in uploading Suffolk sheep breed data to NSIP.
For Sub-objective 1C, the third year of a three-year study was initiated to evaluate the efficacy of sodium chlorate to reduce fatal diarrhea in neonatal lambs and mastitis in ewes. Sodium chlorate can greatly decrease Enterobacteriaceae organisms (e.g., E. coli and Salmonella) that cause fatal diarrhea in newborn lambs. Lamb health, survivability, and growth were monitored, and mastitis incidence was quantified in the lactating ewes.
Substantial progress was made towards completing Objective 2, determining the sheep-production and ecological value of using sheep grazing to improve sage grouse-nesting habitat in recently-burned mountain big sagebrush steppe. In big sagebrush steppe (rangeland) that is burned, recovery of shrubs is important for the sustained health of the ecosystem. Fire is an important component of mountain big sagebrush communities. However, too much fire (e.g., every year) will destroy big sagebrush communities and too little fire (e.g., complete fire suppression for decades) is also detrimental to the ecosystem. Wildlife (e.g., sage grouse) and optimal livestock production are dependent upon healthy big sagebrush communities. The third year of sheep grazing treatments were applied in a mountain big sagebrush community that was burned in 2008/2009. Total vegetation, by species, was quantified and herbivory of sagebrush was monitored.
Accomplishments
1. Facilitating genetic improvement of the Polypay sheep breed. Profitable producers strive for genetic improvement in their livestock. One way to achieve this is through use of estimated breeding values (EBV), which indicates an individual’s genetic potential for a trait. The accuracy of EBV is dependent upon the number of production records from the individual of interest as well its relatives (offspring, siblings, parents, etc.). Further, confidence in comparing EBV across flocks is greatly enhanced if flocks have strong genetic connectedness (i.e., share ancestry). Unfortunately, such kinship data is often lacking in the sheep industry, resulting in EBV of subpar accuracy. In an extensive effort to improve the utility of EBV for the Polypay sheep breed, ARS researchers at Dubois, Idaho, collected, formatted, and uploaded 17,379 records to the National Sheep Improvement Program, which is the primary database used for calculating EBV for U.S. sheep. The large volume of records and genetic connectivity to other flocks will result in increased accuracy of EBV and improved confidence in comparing EBV across flocks for the Polypay breed, thus enabling producers to meet their genetic improvement goals sooner.
2. Mitigating the burden of rearing orphan lambs. The annual number of lambs born to a ewe (female sheep) greatly influences profitability of range sheep enterprises. In highly prolific flocks, some ewes may give birth to more lambs than they can successfully rear, which is the case for triplet-bearing, wool-type ewes managed in rangeland systems of the U.S. West. Often, producers are forced to orphan at birth and artificially rear (e.g., bottle feeding) extra lambs, which drastically erodes profitability. ARS scientists in Dubois, Idaho, have developed a solution that involves leaving triplet lambs with the birth ewe until the lambs are approximately 35 days of age, then immediately weaning one of the triplet lambs. This method reduces the burden of artificially rearing orphan lambs and thus, maintains profitability. Such management solutions are critical for producers to efficiently improve flock lambing rates without suffering from the economic and laborious burden of artificially rearing orphan lambs.
Review Publications
Sprinkle, J.E., Taylor, J.B., Clark, P., Hall, J.B., Strong, N.K., Roberts-Lew, M. 2019. Grazing behavior and production characteristics among cows differing in residual feed intake while grazing late season Idaho rangeland. Journal of Animal Science. 98(1):1-9. https://doi.org/10.1093/jas/skz371.
Henslee, D., Yelich, J., Taylor, J.B., Ellison, M. 2019. Avoidance of Phenylthiocarbamide in mature Targhee and Rambouillet rams. Translational Animal Science. 3(4):1194-1204. https://doi.org/10.1093/tas/txz125.
Murphy, T.W., Stewart, W.C., Smith, C.G., Taylor, J.B. 2018. Effects of late gestation shearing on body weight, feed intake, and plasma metabolite concentrations in Rambouillet ewes managed outdoors during winter. Animal. 13(3):600-605. https://doi.org/10.1017/S175173111800191X.
Page, C.M., Van Emon, M.L., Murphy, T.W., Larson, C.K., Berardinelli, J.G., McGregor, I.R., Taylor, J.B., Stewart, W.C. 2019. Effects of zinc source and dietary concentration on serum zinc concentrations, growth performance, wool traits, and reproductive characteristics in developing rams. Animal. 14(3):520-528. https://doi.org/10.1017/S1751731119002180.
