Estimates of direct and maternal covariance functions for growth of Australian beef calves from birth to weaning

Abstract

-Records for birth and subsequent, monthly weights until weaning on beef calves of two breeds in a selection experiment were analysed fitting random regression models. Independent variables were orthogonal (Legendre) polynomials of age at weighing in days. Orders of polynomial fit up to 6 were considered. Analyses were carried out fitting sets of random regression coefficients due to animals' direct and maternal, additive genetic and permanent environmental effects, with changes in variances due to temporary environmental effects modelled through a variance function, estimating up to 67 parameters. Results identified similar patterns of variation for both breeds, with maternal effects considerably more important in purebred Polled Herefords than a four-breed synthetic, the so-called Wokalups. Conversely, repeatabilities were higher for the latter. For both breeds, heritabilities decreased after birth, being lowest when maternal effects were most important around 100 days of age. Estimates at birth and weaning were consistent with previous, univariate results. covariance functions / early growth / modelling / beef cattle / maternal effects

Trajectory of body weight of performance tested dual-purpose bulls

“…Therefore heritability also increased ( Figure 5). The results are in agreement with Meyer (2002). There were no differences in heritability between the simple and weighted analysis (Figure 5).…”

“…This can be solved by weighted analysis or by modelling the curve for the residual. Meyer (2001) described variance by a polynomial function of higher degree to alter variance in dependence on age. The variance function has a part of measurement error and a part of polynomial function.…”

Modelos De Regressão Aleatória Para Característica De Crescimento Em Bovinos Da Raça Guzerá

“…Entretanto, as estimativas para os pesos aos 120 (P120), 210 (P210), 365 (P365) e 450 (P450) dias de idade também foram expressivas, com tendência de aumento (0,38, 0,32, 0,47 e 0,53, respectivamente). Comportamento similar foi relatado por Sousa Júnior et al (16) para a raça Tabapuã, por Meyer (19) para bovinos da raça Hereford e por Albuquerque e El Faro (20) para a raça Nelore. Esses autores reportaram redução nas estimativas de herdabilidade direta após o nascimento, aumentando com o avanço da idade do animal.…”

Computing approximate standard errors for genetic parameters derived from random regression models fitted by average information REML

“…However, there have been no attempts to quantify the accuracy of such estimates for different parts of the trajectory from RR analyses using residual maximum likelihood (REML) methods. In contrast, Meyer [9] published confidence intervals of genetic parameter estimates derived from Bayesian analyses using Gibbs sampling. With REML estimation by the average information algorithm, approximate variances of variance components are obtained from the inverse of the information matrix.…”