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Sheep research: UW professor shares sheep research findings and gives overview of current work

by Wyoming Livestock Roundup

Casper – The Wyoming Natural Resource Rendezvous Convention and Trade Show at the Ramkota Hotel and Convention Center in Casper Dec. 5-8 hosted a variety of speakers, breakout sessions, committee meetings, a trade show and luncheon banquets. 

During the event, University of Wyoming (UW) Department of Animal Science Assistant Professor Cody Gifford shared findings of several sheep research projects with attendees, as well as provided information on current research projects. 

Sheep study 

One UW research study titled “Effects of harvest season on carcass characteristics of lamb in the Intermountain West” looked at hot carcass weight (HCW), 12th rib fat thickness (RFT), body-wall thickness, longissimus muscle area, U.S. Department of Agriculture yield grade (USDA YG), percentage closely trimmed retail cuts and calculated yield grade (Calc YG). 

Data from 10,027 lamb carcass characteristics was collected from two commercial processing plants on 30 separate dates over the course of May 2018 through May 2019. Measurements were collected between the 12th and the 13th rib of the lamb carcasses.

Carcasses of lambs slaughtered in the spring had a 3.4 kilograms or 8.5 pounds heavier HCW than lambs slaughtered in the summer. Measurable 12th rib fat and Calc YG tended to be greater in the spring compared to the summer.

“Of the total lambs harvested every year, only about half of them are graded,” mentioned Gifford. “One reason is because some small plants often don’t have USDA graders. Another reason is, even in large plants, there are a portion of ungraded lambs.” 

He further noted ungraded lambs are still inspected and go into commerce as a healthy, safe-to-eat product, but they are not receiving a grade because they either have lower quality factors or because they may be in a yearling or mutton maturity classification. 

“Grading is a voluntary program and is not required. These are two reasons why the industry may only see roughly 50 percent of the lambs in inspected facilities receive a USDA grade through the voluntary USDA grading program,” he shared. “Of those graded, roughly 92 percent of them are typically graded as Choice, and the remaining seven to eight percent are typically graded as Prime.” 

There are five quality grades the industry can utilize. They include Prime, Choice, Good, Utility and Cull, but primarily Prime and Choice are utilized among graded lambs. 

Of the lambs evaluated in this study, around 892 lambs were ungraded, Gifford said.

Overall graded lamb carcasses exceeded commercial processing plant preferred HCW by five percent and industry acceptable fat thickness by 25 percent, and 70 percent of lamb carcasses exceeded six millimeters of fat thickness or nearly 0.25 inches. 

Based on current findings, the season of slaughter influenced HCW and USDA YG but no other carcass characteristics of lambs slaughtered in the Intermountain West. In the study, over 43 percent of the carcasses surveyed were assigned a USDA YG of four or five, indicating industry-wide room for improvement. 

Results of the study indicated lamb carcasses sampled in commercial processing plants in the Intermountain West during 2018 and 2019 were representative of recent carcass trends throughout the U.S. and were heavier and fatter than both domestic and international industry preferences. 

Current work:
backgrounding study

With the bulk of lambs being born in the spring, UW Graduate Student Clara Ritchie started work on a backgrounding study. 

“What this project has focused on is taking UW flock lambs born through March and April, get them weaned and split them into two groups,” shared Gifford. “One group was put on a high-energy diet and the other group was put on a high meadow pasture. They grazed through the entire fall before they were brought back to a high-energy diet.”

In contrast to typical backgrounding scenarios, this study was not designed to get lambs to increase a lot of weight, but rather to answer the question if lambs can be grazed and maintained before putting them on the same high-energy diet while not making them overly fat, he explained. 

“The intent of this study was to provide a potential management option for producers resulting in carcasses that would be more competitive for customers looking for a specific carcass weight, size and composition,” said Gifford. “Often, when producers background animals, they hope they will gain weight on a cheaper feed source, but in this case, we wanted them to maintain.”  

All of the lambs used in this study were born in March and April. Both sets of animals were fed for 66 feedlot days – the first group in the fall and the second group in the spring. 

“The backgrounded lambs ended up being trimmer,” he shared. “A couple of possibilities as to why this may have happened is the lambs may have been metabolizing fat during the fall, focusing more of the nutrition of their diet on muscle growth and less on fat growth. The other reason may be because backgrounded lambs tended to be more efficient once they got to the high-energy diet. It took them less total feed over the feeding portion, and as a result they ended up being trimmer in the end.” 

“If we think about total cost per pound per gain between the conventional feedlot lambs and the backgrounded lambs, it came out to be 58 cents per pound per gain versus 44 cents per pound of gain during the feedlot phase,” he said. 

Current work: flavor study

In this study, flavor attributes were also evaluated. They found, from a flavor standpoint, there weren’t many differences between the two groups, and cooked loin samples were very tender from both groups. He noted a few differences in the backgrounded lambs in regard to higher fat levels, but it didn’t influence the eating quality of the meat. 

Gifford and UW Extension Associate Professor and Sheep Specialist Whit Stewart are continuing to work on several other studies. One of the studies includes this same concept, while also growing the lambs to a heavier weight. 

“We’re repeating the same project, but in this case, both in the fall and the spring groups we will be pushing them to 160 pounds,” said Gifford. “This will truly be a test to see if things match up to the first study or if we see differences between these groups of lambs.” 

Current work: blockchain technology

UW Master Candidate Student Courtney Newman is also assessing blockchain technology with a three-component project looking at animal health and movement, wool traceability and applications in the meat industry. This study is focused on whether more information about the live animal on the label is useful information to the consumer, and part of her study involves a consumer survey. It can be completed by following   

UW is also conducting several surveys assessing consumer opinions and perceptions about using blockchain technology. The 2022 Ram Benchmarking Survey looks to build a database of baseline costs associated with raising high-quality rams. This survey can be completed by visiting 

Another survey, 2022 Cost of Production Benchmarking Survey, is aimed to help sheep producers understand their productivity and cost of production and how it compares to operations of similar size, which can be found at

The intent of all surveys is to help strengthen the U.S. sheep industry.

“There’s far more sheep research currently happening at UW,” Gifford concluded. “There’s additional projects currently happening and several planned for the next couple of years that will be ongoing. We hope to host additional field days to get user-friendly information out to stakeholders and hopefully receive feedback on challenges we haven’t thought about that we need to focus research efforts on.” 

Brittany Gunn is the editor of the Wyoming Livestock Roundup. Send comments on this article to 

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