Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/5/2009
Publication Date: 7/12/2009
Citation: Van Raden, P.M., Tooker, M.E., Cole, J.B. 2009. Can you believe those genomic evaluations for young bulls?. Journal of Dairy Science. 92(E-Suppl. 1):314(abstr. 279).
Technical Abstract: Breeders began selecting on official genomic tests for U.S. Holstein and Jersey bulls, cows, and heifers in January 2009. Statistical properties of genomic evaluations, traditional evaluations, and parent averages were validated using data from November 2004 to predict January 2009 daughter merit, weighted by reliability of 2009 data. The validation used 1,611 young and 4,422 proven Holstein bulls in 2004. The top 20 young and top 20 proven bulls were selected based on 2004 traditional or genomic net merit. To determine if selection was effective, means from 2004 and 2009 data were compared after subtracting $155 for the 2005 base change. Mean 2009 daughter merit was $403 for the young bulls selected on parent average, $516 for young bulls selected on genomic evaluation, $380 for proven bulls selected on traditional evaluation, and $464 for proven bulls selected on genomic evaluation. Thus, actual merit was highest for genomic tested young bulls and lowest for traditionally evaluated proven bulls. Evaluations in 2004 were higher than average daughter merit in 2009 for all 4 groups, with respective biases of $273, $130, $71, and $29. Regressions of 2009 daughter deviations on 2004 evaluations were expected to be 1.0 across all bulls but were 0.64, 0.74, 0.93, and 1.12 for the 4 groups. Thus, evaluations of young bulls are biased, but the bias is less with genomic tests than with parent average. Adjustments are needed such as further limits on phenotypic deviations or decreases in heritability to decrease bias, particularly for traditional parent average. Selection using traditional or genomic evaluations had only small effects on average relationships among selected animals. The correlation with expected future inbreeding was slightly higher for young bull parent average than for the genomic evaluation (0.21 vs. 0.13). Breeders should greatly increase use of the best young Holstein bulls because their merit already exceeds that of the best proven bulls, and advantages of young bulls over proven bulls will increase as more young animals are tested.