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Virginia Polytechnic Institute and State University, Blacksburg 24061
ABSTRACT
Holstein cows (297) in five Virginia Institutional Breeding Project herds were evaluated subjectively by a linear scoring system and were measured objectively for related physical components of conformation. Repeatabilities for physical traits ranged from 45% (rear leg angle) to 90% (stature) with most traits exceeding 70%. Subjectively scored linear traits were generally skewed negatively with few cows scored in the lower 40% of scores for rump, side view (slope), rear legs, side view (set), strength of body, and dairy character.
Multiple squared correlations for models predicting linear scores of individual cows from their related physical traits ranged from .09 to .68, with a majority between .30 and .50. Correlations for identical models, of means of linear scores and physical traits, ranged from .45 to .97, with most exceeding .70. Regressions indicated relationships between linear scores and physical traits were as expected and, in general, were homogeneous between classifiers. Changes in physical traits per point change in linear scores were small.
The linear type evaluation system examined distinguished with reasonable accuracy among cows the differences in their physical components of conformation. However, improvements in the system may be possible by redescribing
1 Published with approval of the 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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P. O. Boisot, S. L. Rodriguez-Zas, and R. D. Shanks Repeatability of Objective Measurements on the Rear Legs of Dairy Cows J Dairy Sci, September 1, 2002; 85(9): 2344 - 2351. [Abstract] [Full Text] [PDF] |
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