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U of I, USDA collaborate on sheep genetic research

By John O’Connell

University of Idaho

Scientists with University of Idaho and the U.S. Department of Agriculture have collaborated on genetic research to help sheep ranchers improve sheep longevity and better utilize their flocks in targeted grazing to benefit rangeland health.

The U of I scientists, Brenda Murdoch and Melinda Ellison, both co-authored separate studies with Bret Taylor, research lead of the USDA Agricultural Research Service’s U.S. Sheep Experiment Station in Dubois.

The studies, which were funded by USDA, extrapolated data from the facility’s long-term records, as well as from experiments they conducted with the Dubois flock. 

The ewe longevity and herbivory studies are among several collaborative research projects involving U of I and USDA researchers in Dubois aimed at helping the sheep industry improve environmental stewardship, profitability and productivity, as well as aiding land management agencies with mitigating rangeland risks from invasive weeds, climate change and catastrophic wildfire.

For the ewe longevity study, Murdoch’s team analyzed molecular records of more than 1,000 sheep dating back to 2009. They studied a host of traits, such as milk production, lambing success, dental health and body condition, that strongly correlate with ewe survival.

From a review of more than 500,000 markers, they ultimately identified 32 important genetic variants influencing ewe life expectancy, including several traits associated with lambing success and seven variants that are directly related to increased longevity.

From records of animals that left the herd early, they also identified variants correlated with poor longevity. Knowledge of the genetic variants should help producers make informed breeding and management decisions.

“We look at genetic variants and we see which ones are associated with traits we want to select for or against. Something we may want to select against might be a disease,” Murdoch said. “Lambing success is a big part of ewe longevity.”

The average age of ewes in the study was 6 years old. Of the common sheep breeds they evaluated, Rambouillet had the highest longevity, persisting in the herd for a full year longer than the breed with the shortest longevity, Suffolk. 

Murdoch and Taylor plan to publish the study findings soon and are in the process of finalizing a manuscript.

Montana sheep rancher Ben Lehfeldt, who is vice president of the American Sheep Industry Association, heard Murdoch present about the ewe longevity research during a June 6 meeting of researchers and industry leaders in Dubois.

“From a producer point of view, we’re always looking for practical research that will translate to helping us raise better sheep and be more economical,” Lehfeldt said. “Dealing with longevity, if you can have a ewe that stays around for an extra year, that’s worth how many pounds of lamb and wool?”

Working with Taylor, Ellison started a series of studies in 2016 that have been published and are still ongoing about sheep grazing preferences. They’ve tested whether certain rams would avoid eating feed or water treated with a bitter-tasting compound.

“One of the things sheep are used for in a lot of cases is targeted grazing. It’s becoming more common to have sheep target a specific plant for rangeland health,” Ellison said. “If we have a certain type of noxious weed that has a bitter flavor, animals that don’t have an aversion to a bitter flavor may be more willing to graze those plants.”

Regarding water treated with the bitter compound, some rams strongly avoided drinking it while others were undeterred.

Though rams didn’t avoid feed with the bitter flavor added, some of them exhibited behavioral changes after consuming it, such as pawing, pacing and butting.

Ellison suspects feed may have other flavors that mask the bitterness, while the bitterness is likely easier for sheep with bitter taste receptors to detect in water. Additional research will also be needed to assess if certain bitter plants give sheep a stomachache, posing an additional barrier for targeted grazing.

Working with Ellison and Taylor, Murdoch conducted genetic analysis of rams involved in the bitter-water experiment. She sequenced through 25 genes related to taste reception in sheep to identify variants associated with non-tasters and super-tasters of bitterness.

“Rangeland managers, including ranchers and government agencies such as Forest Service, desperately need effective tools to manage vegetation at a landscape scale,” Taylor said. “If we can better understand and better predict the types of plants sheep will consume, as well as determine the heritability of herbivory preference, we could develop sheep flocks with specific grazing traits, which can be used to manipulate vegetation at a landscape scale towards important rangeland management goals.”

Taylor has been especially impressed with the U of I graduate students who have participated in collaborative research studies in Dubois. He’s worked with U of I graduate students who have presented at scientific meetings and won awards for their efforts.

“One thing that is just extraordinary about the work of both Brenda and Melinda is they attract very high-quality graduate students,” Taylor said. “Since we are USDA and we are a pure research unit, having intelligent, hardworking graduate students is really good for us because they produce results and they publish.”