Benchmarking performance in Targhee sheep in development of a genetic reference flock

Abstract

The Targhee breed is important to range sheep production in the Western U.S. The objective of this research was to integrate industry sires participating in national genetic evaluation through the National Sheep Improvement Program (NSIP) into the U.S. Sheep Experiment Station (USSES) flock, where the breed originated, to benchmark sire performance. Estimated breeding values (EBV) of industry sires (n = 16) and USSES sires (n = 12) from the 2023 NSIP Targhee genetic evaluation differed (P < 0.05) only for the NSIP Number Born EBV. This difference, and small (nonsignificant) differences favoring industry sires for maternal weaning weight, yearling fiber diameter, and yearling staple length EBV also resulted in greater (P < 0.05) Western Range Index scores for industry sires. The performance of sires’ direct progeny born 2016 to 2018 was compared for 17 traits. After data cleaning, there were 664 progeny (417 from industry sires and 247 from USSES sires) with 146 to 664 records per trait. Least squares means differed (P < 0.05) for grease fleece weight, side fiber diameter, and britch fiber diameter in favor of the industry sires. Production traits were measured from the progeny and other retained descendants of both sire genetic groups from 2016 through 2022. After data cleaning, there was a range of 1,138 to 1,493 records per trait. A three-generation pedigree was constructed and the proportional assignment of each lamb to each genetic group (e.g., 0.5 industry, 0.5 USSES) was included in an augmented relationship matrix. A univariate animal model was fitted for each lamb trait and a repeated measures model for each of the three ewe traits was fitted to estimate variance components and predict breeding values. Genetic group solutions did not differ (P > 0.05) for any of these traits but provided a means by which to compare the two groups. Establishment of a Targhee genetic reference flock at USSES has been initiated, which can be used to address issues of importance to the industry.