Genet. Sel. Evol.
Volume 38, Number 6, November-December 2006
|Page(s)||617 - 635|
|Published online||28 November 2006|
Genetic heterogeneity of residual variance in broiler chickensSuzanne J. Rowea, Ian M.S. Whitea, Santiago Avendañob and William G. Hilla
a Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, UK
b Aviagen Ltd., Newbridge, Midlothian, EH28 8SZ, UK
(Received 31 January 2006; accepted 9 June 2006; published online 28 November 2006)
Abstract - Aims were to estimate the extent of genetic heterogeneity in environmental variance. Data comprised 99 535 records of 35-day body weights from broiler chickens reared in a controlled environment. Residual variance within dam families was estimated using ASREML, after fitting fixed effects such as genetic groups and hatches, for each of 377 genetically contemporary sires with a large number of progeny (>100 males or females each). Residual variance was computed separately for male and female offspring, and after correction for sampling, strong evidence for heterogeneity was found, the standard deviation between sires in within variance amounting to 15-18% of its mean. Reanalysis using log-transformed data gave similar results, and elimination of 2-3% of outlier data reduced the heterogeneity but it was still over 10%. The correlation between estimates for males and females was low, however. The correlation between sire effects on progeny mean and residual variance for body weight was small and negative (-0.1). Using a data set bigger than any yet presented and on a trait measurable in both sexes, this study has shown evidence for heterogeneity in the residual variance, which could not be explained by segregation of major genes unless very few determined the trait.
Key words: broiler chickens / body weight / genetic variance / environmental variance / heterogeneity of variance
© INRA, EDP Sciences 2006