Sheep Industry News February 2024

Inheritable Traits & Selection Indexes CAT URBIGKIT A t the Genetic Stakeholders Forum’s all-day session during the ASI Annual Convention in Denver, retir ing professor and genomics expert Dr. Ron Lewis of the University of Nebraska-Lincoln reminded producers to not overlook the basics when utilizing new technologies. animals that perform well under these conditions is key. But the challenge is that 44 percent of ewes in the United States are culled prematurely for reasons other than age, 7 percent of the lamb crop dies each year from non-predator related causes, clinically health ewes with high somatic cell counts in their milk cause economic losses of $19 to $32 per ewe, and more than 20 percent of mature ewes in most commercial flocks have been diagnosed with high somatic cell counts.

In establishing breeding goals, he cautioned that selecting for more traits simultaneously results in less genetic progress in each individual trait. Producers also need to be cautious in deciding which traits to include in their breeding goals, as only economi cally relevant traits should be included. The solution is to look at not individual traits, but selection indexes that have been devel oped for use by producers in the United States. U.S. Meat Animal Research Center Research Geneticist Dr. Tom Murphy explained that a selection index optimally weighs individual traits by their relative importance toward a defined breeding objective. He noted a favorable Estimated Breeding Val ue for one trait can override a less desirable EBV in another trait. To create a selection index, first the breeding objective must be defined. A productivity index seeks to improve an unmeasured composite trait – such as total weight weaned or lean growth. An economic index seeks to improve the profitability in a defined production system – as in returns and variable costs. The next step is to identify traits that are reasonably important toward achieving the breeding objective. These are dependent upon the production/marketing system, and each additional trait reduces individual trait gains, Murphy explained. A Carcass Plus Index developed by LambPlan and vetted by the National Sheep Improvement Program is a desired gain index that promotes high growth and muscling while maintaining lean ness of meat but doesn’t consider costs and returns. The Maternal Productivity Index simultaneously improves multiple compo nents of maternal ability but also doesn’t consider costs and returns. The Western Range Index developed by NSIP predicts the genetic merit for profitability in a Western range environment but needs to be updated to current economic conditions. Murphy said a well-designed selection index is the most ef ficient means of improving multiple traits simultaneously, and that improvements will continue to be made as the indexes are revisited and updated to meet the needs of American producers. Lewis then led a session on improving robustness and climatic resilience in the American sheep population through genom ics. He explained that the industry consists of a variety of breeds raised in a range of geographies that differ in both climatic conditions and management practices, and that breeding robust

Dr. Ron Lewis University of Nebraska-Lincoln, Sheep GEMS Project

Lewis explained that climatic resilience and robustness must take into account environmental factors (location, weather and management practices) as well as gastrointestinal health and ewe longevity, and udder health and lamb survival factors. Such traits are largely absent in American sheep genetic evaluations, but research is currently underway to address these factors through the Sheep GEMS (Genetics, Environment, Management, So cioeconomics) Project. Students Hilal Yazar Gunes and Arthur Rocha Oliveira are examining current management practices in varied production systems and environments, and the impact of genomic information inclusion in genetic evaluation, including assessing the impact of missing pedigree information or misiden tified sires to EBV accuracy. The session also included a roundtable of updates from the nation’s Agricultural Research Service stations, from alternative parasite control methods in Arkansas, to udder health research in Nebraska, and comparing breed performance using the Western Range Index in Idaho, with presenters providing highlights of their work to support and improve the American sheep industry. The Genetics Forum concluded with acknowledgment of Lewis for his years of dedicated effort to improving the genetic health of the nation’s sheep flocks, as he is retiring from his posi tion at the University of Nebraska this year.

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