Overall Classification as a Selection Criterion for Improving Categorically Scored Components of Type in Holsteins

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Abstract
The efficiency of final classification score as a selective criterion for improving genetically the 12 components of type descriptively classified by Holstein-Friesian Association of America was examined. Comparisons were between selection on final score and direct selection on each descriptive trait, and between selection on final score and selection on several least squares indexes including descriptive traits. Procedures for adjusting phenotypic and genetic correlations between categorically scored descriptive traits for the effects of discontinuity and skewness were determined from theory and were tested by computer simulated data. Final classification score was an efficient selective criterion for improving individual descriptive components of type and several linear combinations of components. Expected correlated responses in descriptive traits to selection on final score ranged from 53-124% of the expected direct response. Additionally, selection on final score was expected to be 80-119% as efficient as index selection for improving genetically 7 linear combinations of type traits.