Sheep Industry News August 2023

determine animals’ status for five genetic conditions: ovine progressive pneumonia susceptibility, scrapie susceptibil ity, double muscling, callipyge, and booroola FecB. We have already released those results to participating breeders. The extra cost associated with obtaining these specific genetic conditions as independent tests exceeds the cost of the 50K array by itself.

values when incorporating genomic information depend in part on the number of animals with both performance and genotype data within a breed. Those individuals form a breed’s reference population. The reference population needs to capture the full genetic diversity of a breed, which is being accounted for in the design of the genotyping strat egy underway in Sheep GEMS. Breeds differ in their genetic diversity due to factors such as past selection, population size, breeding policies and geo graphic distributions. Due to these factors, genetic variation is often lost through time. This loss in diversity translates into the number of individuals effectively participating in producing the next generation, or the effective population size (Ne). The Ne is often substantially smaller than the actual number of individuals in a population or breed. By es timating the Ne of a breed – our proxy for the extent of its genetic diversity – we can approximate the size of the reference population needed to achieve different levels of accuracy from genomic prediction. Estimating the Ne and other genetic diversity measures also helps us to establish a baseline to monitor genetic diversity as we move forward. Using more than 92,000 pedigree records available through NSIP on Katahdin sheep, we estimated its Ne using a variety of methods. Our minimum estimate was 49. Our

GENETIC CONDITIONS Genetic condition status can be useful in selection (cull ing) and mating decisions, and in marketing programs. However, there is no one-size-fits-all approach. In part, it depends on the economic importance of the genetic condi tion to a sheep enterprise. It also depends on knowing the frequency of various genotypes in a breed and flock, and then using that information judiciously in selection and mating decisions. Culling all animals with less favorable genotypes is seldom the best strategy. From our results (Fig ure 1), there are clear differences among breeds in OPP and PRNP susceptibilities. That information is useful for design ing breeding objectives tailored to the needs and priorities of individual breeds and flocks. Frequencies of genotypes for ovine progressive pneumonia (OPP) and scrapie (PRNP) susceptibilities in Katahdin, Rambouillet, and Polypay sheep.

Frequencies of genotypes for ovine progressive pneumonia (OPP) and scrapie (PRNP) susceptibilities in Katahdin, Rambouillet, and Polypay sheep.

GENOMIC PREDICTION Improvements in the accuracy of estimating breeding

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