Sheep Industry News August 2023

bilities differed appreciably. Heritabilities ranged from 0.30 to 0.37 for BW, from 0.18 to 0.50 for FEC and 0.07 to 0.40 for FAMACHA. Further more, we detected substantial G x E in all three traits. The G x E explained 20 percent, 13 percent and 17 percent of the phenotypic variation in BW, FEC and FAMACHA, respec tively. Although accounting for G x E introduces operational challenges in the design and implementation of breeding programs, doing so would improve the efficacy of selection programs to improve parasite resistance. Returning to the idea that there is no one-size-fits-all so lution for everyone, for parasite resistance and other traits with a G x E, we envision providing a tool whereby breeders can obtain EBVs tailored to their climate and management system. Sheep GEMS is in its early days. Still, our preliminary outcomes are promising. They set the foundation for providing the American sheep industry with methods to improve genetically the robustness and climatic resilience of our flocks. Our success depends on the ongoing support of sheep producers. We look forward to continuing our journey into Sheep GEMS with you. SCIENTIFIC TEAM The Sheep GEMS scientific team is Ron Lewis (Project Director), Luiz Brito (Project Co-Director), Brad Freking, Joan Burke, Tom Murphy, Bret Taylor, Carrie Wilson, Sara Nilson, Brian Arisman, Artur Oliveira Rocha and Hilal Yazar Gunes. ACKNOWLEDGEMENTS We thank the many American sheep associations and breed organizations, NSIP and sheep producers, for their contribu tions to this research. This work is supported by the Organic Agriculture Research and Extension Initiative (grant no. 2016-51300-25723/project accession no. 1010329), and by the Agriculture and Food Research Initiative Competitive Grant (grant no. 2022-67015-36073/project accession no. 1027785), from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

average estimate was 75. Using those values, we approxi mated the accuracy of our breeding value estimates for traits of low (0.1), moderate (0.3) and high (0.5) heritability (Figure 2). With a smaller Ne, a higher heritability, and a larger reference population, accuracies were higher. In Ka tahdins, with more than 10,000 animals already genotyped, we are already achieving fairly accurate genomic predic tions. There are some key take home messages from this re search. First, genetic diversity – and thereby Ne – differs among breeds. Among the aims of Sheep GEMS is to esti mate Ne in all the breeds involved based on more accurate genomic methods. Second, even once the size of a reference population becomes large enough to generate accurate breeding value estimates, genotyping and phenotyping must continue. The reference population must continue to be replenished with animals currently in use in a breed for the benefits of genomic prediction to continue being fulfilled. GENOTYPE BY ENVIRONMENT INTERACTION Resistance to internal parasitism is among the robust ness and climatic resilience traits being considered in Sheep GEMS. Evaluating this trait has challenges. With sheep being raised in various climates and management systems across the United States, the extent of challenge to gas trointestinal parasites varies appreciably. There is also the potential for a genotype by environment interaction (G x E), where individual animals, or sire families, respond dif ferently to the parasite challenge depending on the climate and management practices in which they are raised. Working with NSIP Katahdin producers spread across the United States, we conducted a survey to gather informa tion about their management practices. The survey results were combined with climate data from the National Weath er Service to form nine eco-management groups or clusters to describe production environments more holistically. Using body weights, fecal egg counts and FAMACHA scores on 3,527 Katahdin lambs collected at around 90 days of age, we estimated heritabilities both across and within the eco-management clusters. We also tested for G x E. Across the eco-management clusters, heritabilities of BW, FEC and FAMACHA were 0.36, 0.31 and 0.26, respectively. However, within clusters, phenotypic variances and herita

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