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Title: Cow Adjustments for Genomic Predictions of Holstein and Jersey Bulls

item Wiggans, George
item Cooper, Tabatha
item Vanraden, Paul

Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/8/2010
Publication Date: 6/24/2010
Citation: Wiggans, G.R., Cooper, T.A., Van Raden, P.M. 2010. Cow Adjustments for Genomic Predictions of Holstein and Jersey Bulls. Journal of Dairy Science. 93(E-Suppl. 1):533-34(abstr. 618).

Interpretive Summary:

Technical Abstract: Genomic evaluations are calculated by using values that have been deregressed from traditional PTAs estimating single nucleotide polymorphism (SNP) effects. Previous research indicates that including cow genomic data to calculate SNP effects does not increase reliabilities of genomic evaluations of yield traits. Upward bias in traditional PTA of genotyped cows may be the reason for this. The direct genomic value (DGV) is the sum of an animal’s SNP effects. It should be consistent with traditional PTA and is for bulls. For cows, however, the traditional PTA is higher. To make the cow PTA more like those of the bulls for the yield traits (milk, fat and protein), mean and variance adjustments were calculated. Evaluations were stratified by reliability so cow PTA could be adjusted to be similar to bulls with the same reliability. The variance adjustment was the SD of deregressed Mendelian sampling within reliability group for bulls divided by the value for cows. The mean adjustment is the difference between bull and cow evaluations after variance adjustment. Deregressed Mendelian sampling values were adjusted, and then the deregression was reversed to obtain the corrected PTA. To determine gains in reliabilities, predictions were made for bulls with current evaluations that did not have evaluations in August 2006. The predicted values were compared to the bull’s actual evaluation from January 2010. For Holstein bulls, predictions using cows’ adjusted data were 2.5, 2.8 and 2.1 points higher than those from data without adjustment for milk, fat and protein respectively. Jersey bulls also benefit from cow adjustments with an increase in gains in reliability over parent average of 3.9 points for milk, 5.6 points for fat and 3.5 points for protein. Brown Swiss adjustments could not be evaluated due to low numbers of genotyped cows. Genomic evaluations for Holsteins and Jerseys will be more accurate by better using the information from cows.