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First Classification Score and Length of Herd Life

Dairy Science Extension, The Pennsylvania State University, University Park

H. W. Carter and L. D. Van Vleck

Department of Animal Science, Cornell University, Ithaca, New York

ABSTRACT

The relationship of first score and length of life in the herd was measured in Holstein females two or three years of age at first classification. The regression of herd life (number of times classified) on the first over-all type score (nearly all values were between 65 and 90 points) was 1.7 months. Correlation between first classification score and herd life was approximately 0.2, indicating that less than 5% of the variation in herd life could be attributed to the relationship between first score and herd life.

Differences among herds accounted for about 10% of the total variance in overall type score and in the individual type traits. Differences among sires accounted for from 5 to 8% of the variation in over-all score and in each of the categories (general appearance, dairy character, body capacity, mammary system, fore udder, rear udder, legs and feet, and rump) of the Holstein classification system. Similarly, differences among classifiers accounted for 2 to 6% of the total variance. Classifier variation was greatest in the areas of general appearance, body capacity, and legs and feet.

An analysis of variance components on 7,927 artificially inseminated (AI) sired animals scored from 1958 through 1963 gave a heritability of 0.16 for over-all type score. Heritabilities of over-all score from each of the six years varied widely.