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Journal of Dairy Science Vol. 67 No. 8 1767-1775
© 1984 by American Dairy Science Association ®
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Experimental Linear Descriptive Type Classification1,2,

J. L. Lucas, R. E. Pearson, W. E. Vinson and L. P. Johnson3

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

ABSTRACT

The purpose was to determine if linear descriptive scores ignored age and stage of lactation. Holstein cows in five herds were classified by two evaluators of the Holstein Association. Each herd was scored by a single classifier on experimental linear system. Body measurements logically related to trait descriptions were taken approximately 1 mo later. Body measurements and linear scores were analyzed for age, stage, and interaction effects. Also, linear scores (322) were predicted from related body measurements, and residuals (actual score minus predicted score) were analyzed to determine if classifiers were adjusting subjectively for effects of age and stage of lactation. Classifier and herd within classifier differed for most traits. Age and interactions of age with classifier, indicators of differential age adjustment by evaluators, were significant sources of variation only for residuals of body strength, rear udder width, rump width, and teat placement. The absence of age and stage effects from the residual analyses provides evidence that linear scores for most traits ignored these factors. Residuals also regressed about .2 on final score of the cow. Cows with high final scores were assigned linear scores that were relatively higher than their body measurements would justify.

FOOTNOTES

1 Published with approval of Director of the Agricultural Experiment Station.

2 Supported by grants from the Holstein-Friesian Association of America and National Association of Animal Breeders.

3 Holstein-Friesian Association of America, Brattleboro, VT 05301.






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Copyright © 1984 by the American Dairy Science Association ®.