QTL for several metabolic traits map to loci controlling growth and body composition in an F2 intercross between high- and low-growth chicken lines

1 Institut National de la Recherche Agronomique (INRA, UR83) Recherches Avicoles, Nouzilly 2 INRA, ENVT, UMR444 Génétique Cellulaire, Castanet-Tolosan 3 INRA, UMR1313 Génétique Animale et Biologie Intégrative, Jouy-en-Josas, France 4 Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland 5 Department of Animal and Food Sciences, University of Delaware, Newark, Delaware 6 Department of Poultry Science, University of Georgia, Athens, Georgia Quantitative trait loci (QTL) for metabolic and body composition traits were mapped at 7 and 9 wk, respectively, in an F 2 intercross between high-growth and low-growth chicken lines. These lines also diverged for abdominal fat percentage (AFP) and plasma insulin-like growth factor-I (IGF-I), insulin, and glucose levels. Genotypings were performed with 129 microsatellite markers covering 21 chromosomes. A total of 21 QTL with genomewide level of significance were detected by single-trait analyses for body weight (BW), breast muscle weight (BMW) and percentage (BMP), AF weight (AFW) and percentage (AFP), shank length (ShL) and diameter (ShD), fasting plasma glucose level (Gluc), and body temperature (T b ). Other suggestive QTL were identified for these parameters and for plasma IGF-I and nonesterified fatty acid levels. QTL controlling adiposity and Gluc were colocalized on GGA3 and GGA5 and QTL for BW, ShL and ShD, adiposity, and T b on GGA4. Multitrait analyses revealed two QTL controlling Gluc and AFP on GGA5 and Gluc and T b on GGA26. Significant effects of the reciprocal cross were observed on BW, ShD, BMW, and Gluc, which may result from mtDNA and/or maternal effects. Most QTL regions for Gluc and adiposity harbor genes for which alleles have been associated with increased susceptibility to diabetes and/or obesity in humans. Identification of genes responsible for these metabolic QTL will increase our understanding of the constitutive "hyperglycemia" found in chickens. Furthermore, a comparative approach could provide new information on the genetic causes of diabetes and obesity in humans. quantitative trait locus; glycemia; nonesterified fatty acids; insulin-like growth factor-I; body temperature