| dc.description.abstract | Factors influencing growth traits as calf, and as dam traits
have been analysed. Adjustment factors for such factors were
obtained using Least Squares procedure, and used to correct
records used in parameter estimation. All records were corrected
for sex of calf, age of dam, and season of birth.
Heritability estimates for calf traits were .61±.14, .32±.07,
.38±.09, .43±.14, .70±.17, respectively, for birth weight,
preweaning average daily gain (ADG), 205-d weaning weight,
postweaning ADG, and 365-d yearling weight. Corresponding
estimates foi dam traits were .56±.22, .48±.11, .53±.20, .46±.15,
.66±.30. Within-herd repeatability estimates were .31, .35, .37,
.18, .24, respectively, for dam traits.
Genetic correlations among traits were generally higher than
corresponding phenotypic correlations. All direct-maternal
correlations of calf traits were negative: birth weight (-.21);
205-d weaning weight (-.58); and yearling weight (-.57). The
porportion of maternal (to phenotypic) variance was higher among
traits known to be under large maternal influence (birth weight,
.09; preweaning ADG, .05; weaning weight, .07) than the other
traits (postweaning ADG, .01; yearling weight, .01).
Calving date was suggested as a measure of reproductive
performance. Weight of calf, age of dam, weight of dam, initial
and previous calving dates, and milk production potential were
found to be significantly associated with calving date. Calving
date was found to significantly affect weight and age at weaning,
age at which yearling weights were measured, and postweaning ADG.
Heritability and within-herd repeatability of calving date was
estimated at .19±.06, and .09, respectively.
A method for estimating standard errors of variance ratios,
using logarithmic transformation of the ratios, was proposed and
used in this study. | en |
