Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2002
Publication Date: N/A
Interpretive Summary: Tremendous improvements in commercial broiler chicken production have been made through classical breeding approaches, e.g., body weight, growth rate, and feed efficiency. Immunocompetencies and resistance to disease are determined by individual genes and its interaction with environment. In this study, scientists at the University of Delaware, ARS and Perdue Farms collaborated to investigate genetic factors which control disease resistance in commercial broiler chickens. They compared the production performance parameters of the three commercial broiler pure lines for coccidiosis, Marek's disease and other immune responses. The results of this study clearly demonstrate genetic diversity at various genetic levels and provides valuable information that can be used in future studies for the identification of genetic loci important in economic traits.
Genetic diversity at the major histocompatibility complex (MHC) and non-MHC genes was investigated in three commercial broiler chicken pure lines. The MHC class II and IV loci were evaluated in Souther hybridizations, and molecular genotypes based on restriction fragment length polymorphisms were interpreted from pedigreed families. Four MHC class II and eight class IV genotypes were identified in the broiler lines, and their frequencies differed among the lines. Line-specific MHC genotypes were also identified. The observed heterozygosities (59 to 67%) suggest that the MHC loci are highly polymorphic in the broiler lines. At least 9% of the genetic variation at the MHC was due to line differences; the remainder reflects individual variation. To characterize non-MHC genes, forty-one microsatellite loci located throughout the chicken genome were evaluated in the broiler lines. Genetic variation was also observed at the microsatellite loci for the broiler lines; the number of alleles at a single locus ranged from 1 to 8, and the average number of alleles per locus was 3.5, 2.8 and 3.1 for each of the lines, respectively. This study contributes to our knowledge on the molecular characteristics and genetic structure of a commercial broiler chicken population. Analysis of both MHC and non-MHC genes suggests that there is still sufficient genetic diversity in the broiler lines to continue the progress toward improved broiler chicken production.