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Title: INSULIN-LIKE GROWTH FACTOR 1 GENE POLYMORPHISM ASSOCIATIONS WITH GROWTH, BODY COMPOSITION, SKELETON INTEGRITY, AND METABOLIC TRAITS IN CHICKENS

Author
item ZHOU, H. - IOWA STATE UNIVERSITY
item Mitchell, Alva
item McMurtry, John
item ASHWELL, CHRISTOPHER - NC STATE
item LAMONT, S. - IOWA STATE UNIVERSITY

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2004
Publication Date: 2/1/2005
Citation: Zhou, H., Mitchell, A.D., McMurtry, J.P., Ashwell, C.M., Lamont, S.J. 2005.Insulin-like growth factor 1 gene polymorphism associations with growth, body composition, skeleton integrity, and metabolic traits in chickens. Poultry Science. 84(2):212-219.

Interpretive Summary: Intense genetic selection of broilers has successfully increased growth rate and breast muscle percentage. However, physiological disorders are occurring, such as increased obesity and decreased skeletal integrity. To simultaneously improve production and fitness traits, molecular markers associated with one or both sets of traits may be useful. Insulin-like growth factors (IGF) consist of a family of polypeptide hormones structurally associated with insulin with multiple metabolic and anabolic functions. The IGFs have been shown to regulate body and muscle growth in chickens. The IGF1 gene, therefore, was selected as a biological candidate gene to investigate growth, body composition, metabolic and skeletal traits in chickens. Broiler sires were crossed to dams of two diverse, highly inbred lines. Growth, body composition, skeletal integrity, and hormonal and metabolic factors were measured in the offspring (F2). Strong interactions between the IGF1 gene and genetic background in the two F2 populations suggest that genetic interaction is an important aspect for consideration before using the IGF1 in marker-assisted selection programs. General beneficial effects from the broiler IGF1 gene on improving growth, increasing breast muscle weight, decreasing abdominal fat, and enhancing skeletal integrity indicate that the IGF1 is a useful marker for simultaneous selection for several important broiler traits.

Technical Abstract: Molecular genetic selection on individual genes is a promising method to genetically improve economically important traits in the chickens. A resource population was developed to study the genetics of growth, body composition and skeletal integrity. Broiler sires were crossed to dams of two diverse, highly inbred lines (Leghorn and Fayoumi), and the F1 birds were intermated by dam line to produce broiler-Leghorn and broiler-Fayoumi F2 offspring. Growth, body composition, skeletal integrity, and hormonal and metabolic factors were measured in the F2 population (n = 720). Insulin-like growth factor 1 (IGF1) was selected for study as a biological and positional candidate gene. A single nucleotide polymorphism (SNP) was identified between the founder lines in the IGF-1 promoter region, and a PCR-RFLP assay was developed. A mixed model was used to statistically analyze associations of the IGF1 SNP with phenotypic traits within each F2 cross. The IGF1 SNP had very significant associations with most recorded traits in the broiler-Leghorn F2 cross, but little association in the broiler-Fayoumi cross. Strong interactions between the IGF1 gene and genetic background in the two F2 populations suggest that genetic interaction is an important aspect for consideration before using the IGF1 SNP in marker-assisted selection programs. General beneficial effects from the broiler IGF1 allele on improving growth, increasing breast muscle weight, decreasing abdominal fat, and enhancing skeletal integrity indicate that the IGF1 SNP is a useful marker for a QTL for simultaneous selection for several important broiler traits.