Montana sheep research focuses on growing importance of EPD data, ribeye size

While profitability in-dexes and EPDs have been widely used in many livestock species for years, it is just now becoming more prevalent in the sheep industry.
    According to Lisa Surber, Montana State University wool lab supervisor and research scientist, using a profitability index can help sheep producers group EPDs together to allow them to meet their management goals. It can also be an integral part of genetic evaluation, she added.
    The Targhee growers were the first breed association to embrace EPDs and have been collecting and using the data for about 10 years.
    The profitability index can help producers select for economically profitable traits, like weaning weight and percentage of lamb crop, which determine a large percentage of their income.
    While selecting for these traits can help producers become more profitable, Surber cautions them to avoid putting too much emphasis on yearling weights, which could cause big jumps in mature ewe body size and decrease efficiency.
    In a study at MSU, Surber said production traits of the top 20 indexing yearling Targhee ewes were compared to the bottom 20 indexing yearling Targhee ewes. The top 20 ewes produced 239 more pounds of lamb than the bottom group, which was the equivalent of 12 pounds per ewe.
    “That was a significant amount of weight, and a significant increase using the profitability index,” she said.
Consider the ribeye
    The ribeye is one of the most important cuts of lamb and is important since 80 to 85 percent of sheep income is derived from the meat.
    “We are trying to produce a better lamb chop than our competitors in Australia or New Zealand,” she said. “But, not many of our rams are ultra-sounded to get a feel for ribeye area. Ribeye is mostly visually assessed, which is basically a good guess.”
    She continued, noting, “Ribeye is directly related to dressing percentage, which is the best estimate of carcass merit in lambs. If lambs are sold on a grid, a bigger ribeye means more value.”
    Surber has collected data from the Montana 4-H lamb project during the last five years. The results from this data have been somewhat disappointing, she said.
    “These 4-H lambs should be the cream of the crop for carcasses and above the industry standards,” she explained.
    But the lambs are only producing ribeyes that average 2.8 to 2.9 inches, and less than 40 percent are producing a three-inch eye, she said, adding that sheep producers in the United States promote they are producing three-inch eyes in the commercial sheep industry.
    Surber said she thinks the problem lies with lambs getting bigger, but not improving genetically in their muscle. Loin eye EPDs are also based on depth of muscle measurements instead of the area. Surber mentioned that research needs to be done to determine what impact selecting for ribeye area would have on maternal traits and milk.
    In the future, as more lambs are sold on a grid, ribeye area will be more important, she said.
    “I expect more sires to be measured for it,” she noted.
Collecting EPDs
    Surber said purebred producers need encouragement from commercial producers to collect performance index and EPD information. However, commercial producers may have to pay more for superior sires that have this data available.
    “It takes a strong commitment on the part of the producers over long periods of time to collect this information and improve the accuracy of it,” explained Rodney Kott, MSU sheep specialist. “Most purebred breeders keep records of weaning weights and wool quality. This is just taking it a step further.”
    Gayle Smith is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.