Abstract
Quantitative trait loci (QTL) for abdominal fatness and breast muscle weight were investigated in a three-generation design performed by inter-crossing two experimental meat-type chicken lines that were divergently selected on abdominal fatness. A total of 585 F2 male offspring from 5 F1 sires and 38 F1 dams were recorded at 8 weeks of age for live body, abdominal fat and breast muscle weights. One hundred-twenty nine microsatellite markers, evenly located throughout the genome and heterozygous for most of the F1 sires, were used for genotyping the F2 birds. In each sire family, those offspring exhibiting the most extreme values for each trait were genotyped. Multipoint QTL analyses using maximum likelihood methods were performed for abdominal fat and breast muscle weights, which were corrected for the effects of 8-week body weight, dam and hatching group. Isolated markers were assessed by analyses of variance. Two significant QTL were identified on chromosomes 1 and 5 with effects of about one within-family residual standard deviation. One breast muscle QTL was identified on GGA1 with an effect of 2.0 within-family residual standard deviation.
Highlights
Fat deposition has been investigated for many years in the chicken for its negative impact on feed efficiency, nitrogen retention and lean meat yield [16]
Abdominal fat and breast muscle weights displayed a high phenotypic correlation with 8-week body weight (0.45 and 0.83, respectively); these correlations vanished when data were adjusted for 8-week body weight
quantitative trait loci (QTL) interval mapping analysis was performed on the 309 extreme birds, in each F1 sire progeny for both abdominal fatness (AF) and breast muscle (BM) traits
Summary
Fat deposition has been investigated for many years in the chicken for its negative impact on feed efficiency, nitrogen retention and lean meat yield [16]. The initial resource population was selected on abdominal fat weight of males at 9 weeks of age while body weight was maintained at the same level in both lines In such lines, one can assume that the favourable alleles were fixed in each line during the selection process leading to a more powerful design for QTL analyses. Breast muscle weight and meat yield are both highly heritable [12,23] as demonstrated in the selection of experimental lines [11]. These two traits have been difficult to consider in breeding programmes, and like abdominal fatness, would benefit from advances in molecular genetics.
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