Effect of Age on Estimates of Bovine Growth-curve Parameters

Publisher Website
Google Scholar
Abstract
Estimates of mature weight (A) and rate of maturing (K) determined by asymptotic regression were studied to determine the optimum age range over which estimate of growth curve parameters can be estimated. Quarterly weights of 102 Angus cows at the Plateau Experiment Station were used. The weight-age paremeters were estimated at various ages; all available weights from birth to the specified age were used. The mean estimates of mature weight (A) were 503, 465, 473, 481, 485, 484, and 482 kg for ages 2.5 through 8.5 years, respectively. Mean estimates of rate of maturing (K) were .069, .073, .069, .065, .061 and .061 for ages 2.5 through 8.5 years, respectively. Mean estimate of A and K in which lifetime weights were used, were 497 kg and .056, respectively. Correlations among estimates of A at the various ages were low until cows were 4.5 years old, at which time the correlations tended to stabilize. The same trend was shown among estimates of K; however, correlations among these estimates tended to stabilize at slightly later ages than those among estimates of A. The least-squares analyses of estimates of A and K showed a significant age-reproductive status interaction. The fact that the cow-within-reproductive status component was highly significant indicated significant independent variation available for use in selection programs. The least-squares means of A and K at the various ages with reproductive status held constant indicated a stronger trend with respect to stabilization of estimates at 4.5 years of age with a decline in K as age increased. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.

This publication has 0 references indexed in Scilit: