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.
In support of Objective 1, research continued on increasing lifetime reproduction efficiency, net production yield, and product quality of range-type, wool sheep. For Sub-objective 1.A, a dataset was completed, analyzed, and summarized describing the impacts of using rams (male sheep) of different meat-type breeds to improve offspring (lamb) growth performance, health, and carcass quality. Rams were of the Suffolk and Siremax breeds, and a new breed developed at the ARS location in 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. For Sub-objective 1.B, second-and third-year sheep performance datasets from the Rambouillet, Targhee, and Polypay breeds at the ARS location in Dubois, Idaho, were entered into the National Sheep Improvement Program (NSIP) database. The NSIP is a program that U.S. sheep producers use to evaluate and identify sheep with superior heritable traits and initiate breeding strategies to improve overall sheep production, health, and product quality. For Sub-objective 1.C, the fourth year of a project to evaluate the impact of sodium chlorate, an alternative to antibiotics, to reduce fatal diarrhea in neonatal lambs and mastitis in ewes, was initiated. Sodium chlorate has been shown to 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. In support of Objective 2, research continued on determining the sheep production and ecological value of using sheep grazing to improve sage grouse-nesting habitat in recently-burned mountain big sagebrush steppe (rangeland). In big sagebrush steppe that is burned, recovery of shrubs is important for the sustained health of the ecosystem. Wildlife (e.g., sage grouse) and optimal livestock production are dependent upon healthy big sagebrush communities. The fourth year of sheep grazing treatments were applied in a mountain big sagebrush community that was burned in 2008 and 2009. Total vegetation removed by species was quantified, and herbivory of sagebrush was monitored.
1. Leveraging “taste” for targeted grazing. Human-induced alteration of natural fire cycles threatens the persistence of healthy sagebrush ecosystems that are used to generate high-quality products from livestock grazing and provide critical habitat for wildlife. Burned sagebrush steppe is susceptible to invasive weeds, overdominance of less desirable shrub species, and reduced carrying capacity for both wildlife and livestock. Smart and dynamic grazing strategies are lacking to properly manage sagebrush steppe towards a healthy ecosystem following fire. ARS researchers at Dubois, Idaho, partnered with researchers at the University of Idaho and developed a protocol to identify sheep that can or cannot taste bitter flavors and quantified associated genes that affect a sheep’s ability to taste a bitter-flavored compound. These discoveries may facilitate development of sheep flocks, with defined taste-sensing abilities that can be used (e.g., grazing) to target specific plants that interfere with post-fire recovery of vegetation and subsequently direct sagebrush steppe towards a resilient and robust state.
2. Hastening genetic improvement of U.S. sheep flocks. To improve the overall quality of a sheep flock, it is important to identify parents that have desirable traits (e.g., disease resistance, growth rate) that can be passed on to the young. When estimating the heritable genetic value of sheep, current-day methods are limited to purebred animals within a specific breed. However, the majority of sheep offspring in the United States are crossbred (parents of different breeds), rendering the measurement of inherited traits in the offspring unusable to estimate the genetic value of their parents. ARS researchers at Dubois, Idaho, partnered with researchers at the University of Nebraska-Lincoln, Virginia Tech, and University of New England-Armidale, Australia, and developed quantitative methods that facilitate the use of data collected from crossbred offspring to estimate the genetic value of purebred parents. These discoveries will facilitate the U.S. sheep industry with capitalizing on unused data from millions of crossbred lambs to hasten the genetic advancement of U.S. sheep flocks.
3. Value of newly developed meat-type sheep breeds. One-third of the U.S. sheep inventory is located in the U.S. West, and the majority of these sheep are wool-type breeds. In order to generate greater quality carcasses, sheep producers will cross wool-type ewes (females) with meat-type rams (males) to create offspring with improved meat-trait attributes. Recently, the private sector and ARS researchers at Dubois, Idaho, developed new meat-type composite breeds to express improved meat quality, health, and longevity traits, but the level of improvement achieved in these new breeds had yet to be evaluated. ARS researchers at Dubois, Idaho, partnered with researchers at the University of Wyoming and Virginia Tech and determined that the new meat-type sheep breeds, Siremax and ARS-terminal-sire-composite, generated offspring with comparable performance and quality as offspring generated from the industry-standard Suffolk sheep breed. Information generated from this partnership provides U.S. sheep producers with strategic crossbreeding options to generate specific lamb products preferred by their customer base.
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