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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2007-0348v1 86/5/1081    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Prayaga, K. C. Articles by Gilmour, A. R. Search for Related Content PubMed PubMed Citation Articles by Prayaga, K. C. Articles by Gilmour, A. R.

Estimation of maternal variance components considering cow-calf contacts under extensive pastoral systems

K. C. Prayaga^*,1, J. M. Henshall, D. L. Swain^* and A. R. Gilmour

^* Commonwealth Scientific and Industrial Research Organisation (CSIRO) Livestock Industries, PO Box 5545, Rockhampton Mail Centre, Queensland 4702, Australia; and CSIRO Livestock Industries, Locked Bag 1, Armidale, New South Wales 2350, Australia; and Orange Agricultural Institute, New South Wales Department of Primary Industries, Orange 2800, Australia

¹ Corresponding author: Kishore.Prayaga{at}csiro.au

Traditional methods of variance component estimation for traits under maternal influence consist of partitioning the variance into direct additive genetic, maternal additive genetic, permanent maternal environmental, and error variance components. This partitioning is based on the assumption that each calf is nurtured and fed exclusively by its own dam. However, under extensive pastoral systems, voluntary cross-suckling may occur and could be quantified by using contact loggers recording cow-calf affiliations. A simulation study was conducted to test several variance models for partitioning maternal variation by including information on cow-calf contacts. The results indicated that weighting maternal genetic and permanent maternal environmental effects by the relative time calves spent with particular cows, including their own mothers, is feasible and significantly increased the log-likelihood of the models. However, the interpretation of the variance components in terms of traditional direct and maternal heritability is no longer straightforward. The need for further research and implications for the industry are discussed.

Key Words: contact logger • cow-calf affiliation • maternal genetics • variance component • weaning weight