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Heritabilities of Some Type Appraisal Traits and Their Genetic and Phenotypic Correlations with Production

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

ABSTRACT

Estimates of heritability for 27 type traits and milk and fat production and of genetic correlation of type traits with production were obtained by a within-herd-year analysis of 842 daughter-dam pairs of the Holstein-Friesian breed. Heritability estimates for fat and milk production were higher (.42 and .40) than most reported previously. Most of the type traits studied had heritability estimates not significantly different from zero. Those traits with relatively high estimates were: milking quality, depth of barrel, udder texture, strength of udder attachment, depth of udder, and temperament. Estimates of genetic correlations of type traits with production were inconclusive, owing to lack of confidence in the components of the correlation coefficient.

Phenotypic correlations between 26 type traits and production were estimated. A few other phenotypic correlations thought to be of interest were also estimated. The highest correlation found was between fat and milk production. Type traits which had estimated phenotypic correlations greater than .15 with production were dairy character, withers, depth of barrel, udder shape, depth of udder, and feeding habits. All of these correlations were less than .21.

Selection indexes for breeding value for milk production were computed, utilizing seven variables having the highest heritabilities and phenotypic correlations with production. The index using all seven variables was found to have a correlation with actual breeding value of .58. Using milk production alone to estimate breeding value had a correlation with breeding value of .53. Since selection based on only milk production is nearly as accurate as using seven variables, it appears that in any practical situation selection for milk production could be based on milk production alone.