|Van Vleck, Lloyd|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/1999
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Genetic parameters for mature weight in Hereford cattle were calculated using 8285 records from 2517 cows in a control line and three lines selected for weaning weight, yearling weight, and index of yearling weight and muscle score. Data included cow age (Ag), year (Yr), line (L), pregnancy status (Pg), birth and rearing code (BMR), and calf disposal code e(DSP). Weights were taken each year on three to nine year old cows at three times: brand clipping (BC), before breeding (BB), and palpation for pregnancy checking (PP). Heritabilities were estimated with REML using an animal model with Ag x Yr x L, Pg x L, BMR x L, and DSP x L as fixed effects and direct genetic, maternal genetic, permanent environmental, and residual as random effects. Analyses for BC and BB weights also included interval between calving date and weigh date as a linear and quadratic covariate. Estimates of direct heritability (h2) were .48, .46, and .43, of maternal h2 were .02, .02, and .00, and of fraction of permanent environmental variance (c2) were .24, .29, and .33 for BC, BB, and PP weights respectively when covariance between direct and maternal effects was forced to be zero. When covariance between direct and maternal effects was in the model, direct h2 were .61, .59, and .54, maternal h2 were .05, .05, and .04, and c2 were .17, .21, and .27 for the same weights. Correlations between direct and maternal genetic effects were -.46, -.47, and -.48. Direct h2 is large enough to consider mature weight in breeding programs to optimize economic response to selection. Maternal genetic effects seem to be negatively correlated with direct genetic effects for mature weight although maternal h2 is not large.