Genet. Sel. Evol.
Volume 40, Number 1, January-February 2008
|Page(s)||37 - 59|
|Published online||21 December 2007|
Selection for uniformity in livestock by exploiting genetic heterogeneity of residual varianceHan A. Mulder1, Piter Bijma1 and William G. Hill2
1 Animal Breeding and Genomics Centre, Wageningen University, 6700 AH Wageningen, The Netherlands
2 Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3JT, UK
(Received 30 January 2007; accepted 23 August 2007; published online 21 December 2007)
Abstract - In some situations, it is worthwhile to change not only the mean, but also the variability of traits by selection. Genetic variation in residual variance may be utilised to improve uniformity in livestock populations by selection. The objective was to investigate the effects of genetic parameters, breeding goal, number of progeny per sire and breeding scheme on selection responses in mean and variance when applying index selection. Genetic parameters were obtained from the literature. Economic values for the mean and variance were derived for some standard non-linear profit equations, e.g. for traits with an intermediate optimum. The economic value of variance was in most situations negative, indicating that selection for reduced variance increases profit. Predicted responses in residual variance after one generation of selection were large, in some cases when the number of progeny per sire was at least 50, by more than 10% of the current residual variance. Progeny testing schemes were more efficient than sib-testing schemes in decreasing residual variance. With optimum traits, selection pressure shifts gradually from the mean to the variance when approaching the optimum. Genetic improvement of uniformity is particularly interesting for traits where the current population mean is near an intermediate optimum.
Key words: heterogeneity of variance / index selection / uniformity / economic value / optimum trait
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© INRA, EDP Sciences 2008