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Journal of Dairy Science Vol. 61 No. 1 96-101
© 1978 by American Dairy Science Association ®
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Genetic and Economic Implications of Single Trait Selection for Protein and Solids-Not-Fat1

A. R. Hardie, E. L. Jensen and W. J. Tyler

Department of Dairy Science, University of Wisconsin, Madison 53706

ABSTRACT

Yields of milk, fat, and protein in 2521 Guernsey lactations and milk, fat, and solids-not-fat in 7513 Holstein lactations were used to study genetic and phenotypic relationships. Alternative pricing methods were imposed on expected results of single trait selection as a guide for traits to use in selection plans.

Repeatabilities ranged from .33 to .72. Heritabilities for percentages (.47 to .64) were higher than for yields (.07 to .38). Phenotypic correlations were .86 to .98 among yields, .48 to .52 among percentages, and -.25 to .36 among yields and percentages. Genetic correlations varied from .29 to .95 among yields, .52 to .67 among percentages, and -.75 to .74 among yields and percentages.

Selection for milk yield after one generation should result in 50 to 90% of the genetic gain from direct selection for yields of fat, protein, and solids-not-fat. Selection for fat or protein percentage would decrease milk yield.

Applying various pricing methods to selection programs indicated little difference in gross economic returns from selection within yield traits or within percentage traits. However, 10 to 20% greater gross economic returns could be expected from selecting for yield traits over selecting for percentage traits.

FOOTNOTES

1 Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison.






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Copyright © 1978 by the American Dairy Science Association ®.