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Title: Investigation of country bias in international genetic evaluations using full brother information

Author
item POWELL, REX
item SANDERS, A - UNIV OF FLORIDA
item NORMAN, H

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2008
Publication Date: 7/1/2008
Citation: Powell, R.L., Sanders, A.H., Norman, H.D. 2008. Investigation of country bias in international genetic evaluations using full-brother information. Journal of Dairy Science. 91(7):2885-2892.

Interpretive Summary: The International Bull Evaluation Service combines national genetic evaluation data for dairy bulls in 26 countries in order to translate to each country’s evaluation scale. If the results are biased according to country, there would be substantial financial impact. On average, full brothers are genetically equal, so members of full-brother families in different countries were compared to see if there was a bias by country. Bulls from some countries were significantly advantaged relative to brothers in other countries regardless of country of evaluation scale. It is suggested that national evaluations may favor or disadvantage local bulls, and that bias propagates across all scales.

Technical Abstract: International Bull Evaluation Service Holstein evaluations from May 2005 were examined for country bias by comparing full-brother families. Countries with more than 25 bulls in multi-country, full-brother families were included. The model fit evaluation on the US scale by absorbing full-brother family, and producing solutions for country of most daughters relative to US bulls. Over 20,000 bulls were included in the analysis. The experiment was repeated fitting evaluations on the scales of nine countries other than the US. On all country’s scales, bulls from Australia, Germany, Great Britain, and Japan had an advantage in EBV milk over full brothers from the US and Italy. Bulls from Australia, Great Britain, and South Africa had an advantage in EBV fat. For EBV protein, bulls from Germany, Great Britain, Japan, and South Africa had an advantage, while bulls from The Netherlands were disadvantaged. For SCS, US bulls were advantaged only compared to bulls from South Africa. Significance of biases was similar across country scales of the Interbull evaluations. Cause of biases is unknown; perhaps bias in evaluations of local vs. foreign bulls are present in the national evaluations submitted to Interbull and are propagated throughout national scales in the Interbull results.