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Sources of Variation in Holstein Descriptive Classification Traits¹

Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061

ABSTRACT

First-available classification records of 78,151 Holstein cows in 2117 herds were used to determine the effects of herds, classifiers, and their interaction on the variability of overall type score, scorecard ratings (general appearance, body capacity, dairy character, and mammary system), and the 12 descriptive traits scored in the Holstein-Friesian Descriptive Classification Program. The relative contribution of descriptive traits to final score and scorecard ratings, and differences among classifiers in these contributions also were examined. The percent of variance due to herds and classifiers was small for all traits. Herd by classifier interactions were more important than classifiers for all trains and more important than herds for all descriptive traits. Within-herd standard partial regression coefficients for each classifier indicated that classifiers differed in the emphasis placed on specific descriptive traits in arriving at final score. The descriptive classification program appears to be supplemental rather than superfluous to traditional classifications of final score and scorecard traits.

¹ Published with the approval of the Director of the Division of Animal Sciences.