Genetic associations of growth and lactation curve components in polled Hereford cattle

Abstract

Weight and milk production records of Polled Hereford cows born from 1967 to 1979 were used to fit growth and lactation curves. A multiple-trait, derivative-free, restricted maximum likelihood (MTDFREML) procedure, utilizing a full animal model, was used to estimate variances and covariances for the components of the growth and lactation curves. For the growth curve, W=A+B(1-e-kt) components A, B, and k each had moderate to high heritabilities ranging from .35 to .72. The genetic correlation between growth curve components A and B was positive (.42), whereas the genetic correlations between A and K (-.34) and between B and K (-.74) were negative. In the lactation curve, Yn=n/(aekm) heritabilities of components k and a were .15 and .40, respectively. The genetic correlation between these lactation curve components was -.78.