Genet. Sel. Evol.
Volume 33, Number 5, September-October 2001
|Page(s)||487 - 514|
Genet. Sel. Evol. 33 (2001) 487-514
Estimates of direct and maternal covariance functions for growth of Australian beef calves from birth to weaningKarin Meyer
Animal Genetics and Breeding Unit, University of New England, Armidale NSW 2351, Australia
(Received 30 August 2000; accepted 23 April 2001)
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.
Key words: covariance functions / early growth / modelling / beef cattle / maternal effects
Correspondence and reprints: Karin Meyer E-mail: email@example.com
© INRA, EDP Sciences 2001