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.
