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A Global Scale for Ranking Dairy Bulls Using Blended National Rankings

A Global Scale for Ranking Dairy Bulls Using Blended National Rankings. Rex L. Powell * Paul M. VanRaden Animal Improvement Programs Laboratory Agricultural Research Service, USDA, Beltsville, MD rpowell@aipl.arsusda.gov. Multiple Rankings for Bulls. Holstein International 2001. Objective.

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A Global Scale for Ranking Dairy Bulls Using Blended National Rankings

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  1. A Global Scale for Ranking Dairy Bulls Using Blended National Rankings Rex L. Powell* Paul M. VanRaden Animal Improvement Programs Laboratory Agricultural Research Service, USDA, Beltsville, MD rpowell@aipl.arsusda.gov

  2. Multiple Rankings for Bulls Holstein International 2001

  3. Objective Examine procedures for combining Interbull country evaluations into a common global evaluation Develop base knowledge for next step (sub-global)

  4. Data • May 2001 Interbull evaluations • 27 Holstein population scales • 65,472 bulls with protein data • 24 million daughters

  5. Numbers of Daughters by Countryand Proportion of Global Total

  6. Methods • Evaluations standardized (x-mn)/sd • Global as bull mean, weighted by • Population size • Unweighted • Inverse of population size • Impact on top 100 determined

  7. Relation of National & Global ScaleWithin Birth Year Corr(N,G) = correlation of national with global scale rg= correlation of national scale with other national scales

  8. Relationships of Global Scales Correlations & Common Top 100

  9. Conclusions • Global evaluations highly correlated with national evaluations • Variation between national and global top 100 lists related to mean genetic correlation • Global evaluations robust to weighting procedures (r ~ 1.0)

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