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Title: ACCURACY OF FOREIGN DAIRY BULL EVALUATIONS IN PREDICTING US EVALUATIONS FOR YIELD

Author
item Powell, Rex
item Sanders, Ashley
item Norman, H

Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 6/22/2003
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The addition of foreign daughter data to domestic dairy bull genetic evaluations has been shown to improve prediction of future domestic evaluations in a study of mainly US bulls. This study evaluates the accuracy of Interbull evaluations, based only on foreign daughters, in predicting the latest US yield evaluations, based only on US daughters, thus focusing on foreign bulls. February and August Interbull evaluations from 1995 through 2002 were used. For 652 Holstein bulls, the most recent Interbull evaluations solely from foreign daughter data were matched with February 2003 USDA evaluations based only on US daughters, thus providing a pair of evaluations based on different daughters. For the Interbull evaluations, mean reliability on the US scale was 84% and the mean US reliability for February 2003 evaluations was 78%. Correlations between these Interbull and US evaluations were .88, .82, and .88. for milk, fat, and protein, respectively. Interbull evaluations overestimated the US PTA by an average of 34, 0.4, and 0.7 kg, with standard deviations of the difference of 197, 7.5, and 5.5. Considering only those 153 bulls with US reliability of 90% or higher, correlations were similar to those seen overall for milk (.87) and protein (.88), but higher for fat (.87). Expected correlations were .81 for all 652 bulls and .91 for the 153 bulls. Thus, the actual correlations were higher than expected for all bulls but lower than expected for bulls with the highest US reliabilities. For the higher US reliability bulls, Interbull evaluations underestimated milk, fat, and protein by an average of 7, 0.3, and 0.4 kg, respectively, with standard deviations of differences, 167, 6.2, and 4.6. None of these mean differences between evaluations from foreign and US daughters are large and the correlations indicate that Interbull evaluations based solely on foreign daughters are good predictors of the US evaluations for yield.