Sheep Industry News August 2024

ewe today. For additional perspective, one population of wild mouflon on the sub-Antarctic Kerguelen Islands is estimated to have a 125 percent lamb crop. I’m not trying to poke fun of the average American sheep producer. After all, my small flock of heritage Shropshires raises a 120 percent lamb crop. But they’re also a hobby that is heavily subsidized by my day job. I am not saying we all need a 200 percent lamb crop, there is no one-size-fits-all solution. Some production environments cannot nutritionally support even a 130 percent lamb crop. Terminal sire breeders should put a greater emphasis on growth and carcass traits than ewe reproductive traits. And we all need to balance NLB with the many other economically important traits in sheep production. That’s the beauty of the American sheep industry, you get to decide what genetically superior means for your operation. But how will you get there? Unfortunately, the heritability of a trait pretty much is what it is. Nothing we do is going to make NLB or any other lowly heritable trait a highly heritable trait. Does that mean we just give up on genetically improving lowly heritable traits? No. We just need to modify our traditions and move beyond phenotypic selection as the sole strategy for genetic improve ment. If we only use today’s weather to predict next week’s weather, we can be wildly inaccurate. The only way weather prediction tools get better is by increasing the amount of infor mation they use. Likewise, if we want to be more accurate when identify ing genetically superior sheep, and consequently achieve our unique goals more rapidly, we need as much information as we can get. This is the basis behind estimated breeding values generated by the National Sheep Improvement Program. NSIP EBVs consider more than just the performance of an

individual to infer their genetic merit. Records from siblings, grandparents, cousins and any other type of relative that can be traced through pedigree – and genomics for some breeds – is useful. As mentioned, performance alone can be deceptive if animals aren’t compared on a level playing field. Therefore, performance for all traits considered is first cor rected for non-genetic effects before calculating NSIP EBV. That means a lamb born as a single might have higher genetic merit for NLB than a lamb born as a twin, or the heaviest lamb might not actually have the greatest genetic merit for post weaning weight. Considering corrected performance records from multiple genetic relatives also increases accuracy compared to pheno typic selection. Accuracy is improved even for highly heritable traits but especially for lowly heritable traits. It’s not uncom mon for young ram and ewe lambs enrolled in NSIP to have NLB EBV accuracies > 50 percent, which is far greater than just considering their own birth type (18 percent). All national genetic evaluation programs have limitations, and NSIP is no exception. NSIP EBVs will not tell you if an individual has good feet and leg structure, meets phenotypic breed standards or will pass a breeding soundness exam. This is where you must draw on your expertise and work in tandem with technology to identify genetically superior and pheno typically functional sheep that meet your objectives or those of your customers. When you use NSIP EBVs in this way, you aren’t replacing the tradition of phenotypic selection patiently taught to you by your grandfather, neighbor or livestock judging coach. You’re making your traditions stronger for the next generation. If you have any questions on how you can implement the power of NSIP on your operation, please don’t hesitate to reach out at tom.murphy@usda.gov.

Average lamb crop (number of lambs born/docked per ewe, percentage) by year. U.S. data (black line) is provided by the USDA National Agricultural Statistics Service. Data from the high line (red) and low line (blue) were recorded in a long-term selection experiment at Montana State University. Year-to-year variation has been smoothed out.

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