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Heritability, Phenotypic and Genetic Correlations Between Type Ratings and Milk Fat Production in Ayrshire Cattle^{1, 2,}

Department of Dairy Science and Office of Statistics, West Virginia University, Morgantown

ABSTRACT

Intra-sire-herd variances and covariances of daughters and dams were used to estimate heritabilities and phenotypic and genetic correlations on 8,165 daughter-dam pairs located in 2,924 sire-herd groups. The average of all available type and production records was used.

Heritability estimates for final type rating, components of type, and milk fat production, converted to a single record basis, and 95% confidence limits were as follows: Final type, 0.18±.054; head and neck, 0.27±.062; shoulders and chest, 0.16±.063; middle and loin, 0.16±.066; rump and thighs, 0.22±.064; feet and legs, 0.16±.065; udder shape and size, 0.06±.072; udder attachments, 0.05±.062; teats, veins, and quality, 0.07±.054; general quality, 0.13±.056; breed character, 0.22±.054; and milk fat production, 0.15±.055.

Phenotypic correlations, converted to a single record basis, between the components of type and milk fat production, and final type rating with milk fat production were low, ranging from 0.03 to 0.13. The phenotypic correlations between the various type ratings ranged from 0.14 to 0.62 with a standard error <0.01.

The genetic correlations between the components of type and milk fat production were low, ranging from –0.15 to 0.16, whereas the genetic correlation between final type rating and milk fat production was 0.02. The genetic correlations between the various type ratings ranged from 0.17 to 1.00, with a standard error < 0.10.

¹ Based in part on a thesis submitted in partial fulfillment of the requirements for the degree of Master of Science at West Virginia University.

² Published with the approval of the Director of the West Virginia Agricultural Experiment Station as Scientific Paper No. 703.

³ Present address: Department of Animal Science, Iowa State University, Ames.