Sheep Industry News May 2022

Probing the Genetic Diversity of Suffolk Sheep CARRIE WILSON USDA/ARS National Animal Germplasm Program & RON LEWIS, PH.D. University of Nebraska-Lincoln

• The extent of genetic variability available for a trait (genetic variation). Unfortunately, several of these factors work in opposition to one another. For instance, to be more accurate in our selec tion decisions, we need to collect more performance records on our animals. That takes more time. Consequently, we turn over generations more slowly. Although a higher selection accuracy increases the rate of genetic progress we can achieve, a longer generation interval slows that gain. Advances in molecular-based technologies have provided a way to address this challenge. By combining information from the analysis of an animal’s DNA – so-called genomic data – with its pedigree and performance data, we can more reliably predict its EBV. This allows us to make more dependable selection decisions even in younger animals, increasing selection accuracy and reduc ing generation interval. Genomic enhanced EBV – or GEBV – is the term used for an EBV derived by combining pedigree, performance and genomic data. GEBV have become routine in the beef, dairy and swine industries. For example, in the dairy industry the use of GEBV has increased accuracy of selection to the point that several years of progeny testing is no longer required to prove a bull. Rather than waiting two years for his daughters’ first lactations, the genetic merit of those heifers can now be accurately estimated the day they are born. With that information, bulls can be chosen at young ages reducing the generation interval. With the cost of genotyping decreasing, genomic data is also being used in the genetic evaluation of sheep. In the United States, GEBV were first introduced by NSIP in one breed in October 2021. By using genomic data, we can more accurately identify and se lect genetically superior animals. However, that comes with some risks; it has led to a decrease in genetic variation – or diversity – in other livestock species. Establishing a baseline of genetic diversity in a breed, therefore, is a valuable starting point before obtaining and using GEBV. That was the aim of a collaborative project with NSIP Suffolk breeders funded through an ASI Let’s Grow grant and the U.S. Department of Agriculture's Agricultural Research Service Innovation Fund. In this project, we evaluated the genetic diversity of the Suffolk breed as it is today. NSIP provided pedigree records from more than 64,000 animals. Flock sizes ranged from 9 to 219 with an average of 57.3 sheep per flock. Rams had a maximum of 355 off spring, while ewes had a maximum of 26 offspring. The generation

A ccording to the American Lamb Board Industry Road map, the United States sheep industry needs to promote widespread use of quantitative genetic selection as a tool to cost-effectively produce quality lamb that meets consumer preferences. The National Sheep Improvement Program contributes to that goal by generating and providing Estimated Breeding Values – predictors of an animal’s genetic merit – for growth and carcass traits, among others, to sheep breeders across all sectors of the industry. Classical animal breeding teaches that there are four factors key to making genetic progress: • The accuracy of our selection decisions (selection accuracy); • The percentage of top animals we choose to keep (selection intensity); • How quickly we replace parents with their offspring (genera tion interval); and

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