Abstract
BackgroundComparisons of quantitative trait loci (QTL) for growth and parameters of growth curves assist in understanding the genetics and ultimately the physiology of growth. Records of body weight at 3, 6, 12, 24, 48 and 72 weeks of age and growth rate between successive age intervals of about 500 F2 female chickens of the Roslin broiler-layer cross were available for analysis. These data were analysed to detect and compare QTL for body weight, growth rate and parameters of the Gompertz growth function.ResultsOver 50 QTL were identified for body weight at specific ages and most were also detected in the nearest preceding and/or subsequent growth stage. The sum of the significant and suggestive additive effects for bodyweight at specific ages accounted for 23-43% of the phenotypic variation. A single QTL for body weight on chromosome 4 at 48 weeks of age had the largest additive effect (550.4 ± 68.0 g, 11.5% of the phenotypic variation) and a QTL at a similar position accounted 14.5% of the phenotypic variation at 12 weeks of age. Age specific QTL for growth rate were detected suggesting that there are specific genes that affect developmental processes during the different stages of growth. Relatively few QTL influencing Gompertz growth curve parameters were detected and overlapped with loci affecting growth rate. Dominance effects were generally not significant but from 12 weeks of age they exceeded the additive effect in a few cases. No evidence for epistatic QTL pairs was found.ConclusionsThe results confirm the location for body weight and body weight gain during growth that were identified in previous studies and were consistent with QTL for the parameters of the Gompertz growth function. Chromosome 4 explained a relatively large proportion of the observed growth variation across the different ages, and also harboured most of the detected QTL for Gompertz parameters, confirming its importance in controlling growth. Very few QTL were detected for body weight or gain at 48 and 72 weeks of age, probably reflecting the effect of differences in reproduction and random environmental effects.
Highlights
Comparisons of quantitative trait loci (QTL) for growth and parameters of growth curves assist in understanding the genetics and the physiology of growth
A large number of significant QTL for body weight at specific ages was detected and most of the identified QTL affected growth rate in the preceding and/or subsequent growth stages but overall a smaller number of about 15 chromosomal locations have a substantial effect on growth in this cross
Most of the detected QTL at ages before sexual maturity have been reported in other studies and the results confirm many age specific QTL
Summary
Comparisons of quantitative trait loci (QTL) for growth and parameters of growth curves assist in understanding the genetics and the physiology of growth. Records of body weight at 3, 6, 12, 24, 48 and 72 weeks of age and growth rate between successive age intervals of about 500 F2 female chickens of the Roslin broiler-layer cross were available for analysis These data were analysed to detect and compare QTL for body weight, growth rate and parameters of the Gompertz growth function. Whereas there are many reports of quantitative trait loci (QTL) for body weight and several for rate of growth [2,3,4,5,6,7,8] before sexual maturity, there is relatively little information on QTL for body weight at maturity or growth curve parameters This is partly due to the fact that most meat chickens are slaughtered long before they reach maturity and growth curves cannot usefully be fitted to the data. This might be a useful strategy to minimise weight-related problems associated with rapid early growth, such as skeletal disease, for example
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