Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/1/2006
Publication Date: 10/1/2006
Citation: Zhou, H., Deeb, N., Clover, C.M., Ashwell, C.M., Lamont, S.J. 2006. Genome-wide linkage analysis to identify chromosomal regions affecting phenotypic traits in the chicken. II. Body composition. Poultry Science. 85:1712-1721. Interpretive Summary: Body composition of the chicken is important for many reasons. Breast muscle yield is the most economically valuable part of the broiler. Excess carcass fat is an important issue for many reasons, including consumer health concerns, lower feed efficiency, undesirable by-products, and labor expenses for trimming waste fat during processing. Traditionally it has been very difficult to make improvements in body composition traits. This study was conducted to identify potential genotypic traits associated with body composition. In this investigation a resource population derived from crossing 1 modern broiler sire line with 2 Leghorn and Fayoumi lines of chickens was used. The results of this study identified potential candidate genes for body composition traits. For example, some of the genes identified are associated with the synthesis, transport and storage of lipids. Other genes included with body weight included the genes for many hormones and receptor proteins responsible for cell growth in the chicken. This information will be of interest to poultry geneticists and other scientists.
Technical Abstract: Two informative chicken F2 populations based on crosses between a broiler breeder male line and dams from genetically distinct, highly inbred (>99%) chicken lines, the Leghorn G-B2 and Fayoumi M15.2, have been used for genome-wide linkage and QTL analysis. Phenotypic data on 12 body composition traits (breast muscle weight, breast muscle weight percentage, abdominal fat weight, abdominal fat weight percentage, heart weight, heart weight percentage, liver weight, liver weight percentage, spleen weight, spleen weight percentage, and drumstick weight, and drumstick weight percentage) were collected. Birds were genotyped for 269 microsatellite markers across the genome. The QTL Express program was used to detect QTL for body composition traits. Significant levels were obtained using the permutation test. For the twelve traits, a total of 61 (Gga 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 18, 24, and Z) and 45 (Gga 1, 2, 3, 4, 6, 7, 8, 9, 10, 12, 15, 17, and E46) significant QTL were detected at the 5% chromosome-wise significance level, of which 19 and 11 were significant at the 5% genome-wise level for the broiler-Leghorn cross and broiler-Fayoumi cross, respectively. Phenotypic variation for each trait explained by all QTL across the genome ranged from 3.22 to 33.31% in the broiler-Leghorn cross and 4.83 to 47.12% in broiler-Fayoumi cross. Distinct QTL profiles between the 2 crosses were observed for most traits. Cryptic alleles were detected for each trait. Potential candidate genes within the QTL region for body composition traits at the 1% chromosome-wise significance level were identified from databases for future association study. The results of the current study will increase the knowledge of genetic markers associated with body composition traits and aid the process of identifying causative genes. Knowledge of beneficial genetic variation can be incorporated in breeding programs to enhance genetic improvement through marker-assisted selection in chickens.