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Journal of Dairy Science Vol. 74 No. 2 637-644
© 1991 by American Dairy Science Association ®
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Relationships Among Phenotypic Standard Deviation and Herd Level for Type and Their Effect on Selection Response in United States Holsteins

C. D. Smothers 1, R. E. Pearson 1, W. E. Vinson 1, and D. A. Funk 2

1 Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061
2 Holstein Association, Brattleboro, VT 05301

Phenotypic relationships among various herd parameters, the impact of within-herd SD on selection response, and the relationship of within-herd SD and selection were estimated using first-parity Holstein final scores (1967 to 1986) and hear traits (1983 to 1986), adjusted for age and stage of lactation. Herd mean and within-herd SD for final score demonstrated a strong negative association (r = –.59). Correlations among herd mean final score and within-herd SD for linear traits ranged from –.33 to +.05. Herds were stratified into deciles according to herd mean for final score and subsequently for herd average Predicted Difference type of the herd sires. Within-herd SD for final score declined at a decreasing rate as mean find score increased. The SD for final score declined linearly with increasing mean Predicted Difference type. Small negative trends were noted for within-herd variability of linear traits.

Cows remaining in the herd for higher number of classifications had higher first lactation final score. The magnitude of deviations from the herd mean was useful in predicting within-herd variance suggesting the possibility that selection is partially responsible for decreased within-herd SD.

Regression of daughter contemporary deviation type on her sire's predicted Difference type within 25 mean and SD subclasses indicated selection response differed across herd levels for those parameters. Response to selection on Predicted Difference type was greatest in high mean and variance herds and least in low mean and variance herds. The impact of within-herd SD was at least twice as great as the impact of herd mean. Results suggest that bull proofs for type could be influenced by having daughters in herds that are extreme in within-herd variation.

Key Words: within-herd variance • type scores • selection effectiveness

Submitted on March 26, 1990
Accepted on August 30, 1990




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A. G. Fahey, M. M. Schutz, D. L. Lofgren, A. P. Schinckel, and T. S. Stewart
Genotype by Environment Interaction for Production Traits While Accounting for Heteroscedasticity
J Dairy Sci, August 1, 2007; 90(8): 3889 - 3899.
[Abstract] [Full Text] [PDF]


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Copyright © 1991 by the American Dairy Science Association ®.