Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2000
Publication Date: N/A
Interpretive Summary: Coccidiosis, an intestinal infection caused by intracellular protozoan parasites belonging to several different species of Eimeria seriously impairs the growth and feed utilization of livestock and poultry. Due to complex life cycle of organism and intricate host immune responses to Eimeria, coccidia vaccine development has been difficult. Understanding of basic immunobiology of pertinent host-parasite interactions and host immunogenetics involved in the control of coccidiosis susceptibility/resistance is necessary for the development of novel control strategy. Although many chicken DNA markers have been available during the last 10 years, DNA-based marker selection strategy for avian coccidiosis has not been tried. In this report, ARS scientists, in collaboration with other scientists at University of Delaware and Purdue Farms, Inc., carried out preliminary studies to determine the feasibility of using DNA markers to select for the coccidiosis-resistant chickens in broiler meat-type birds. Preliminary findings indicate that some polymorphic microsatellite markers show substantial correlation with disease resistant traits associated with coccidiosis. These results will provide necessary knowledge for poultry industry to develop logical genetic-based selection strategy for coccidiosis-resistant chickens. If successful, genetic control strategy will reduce economic loss associated with coccidiosis. 1
Two commercial broiler lines were used in an experiment to map quantitative trait loci (QTL) affecting disease resistance, growth, and reproduction traits. Chickens from these lines were genotyped with 27 microsatellite markers to estimate heterozygosity and polymorphism information contest (PIC). Heterozygosity estimated from allelic frequencies was 0.53 and 0.51 1for the two lines; however, heterozygosity calculated from actual counts o heterozygous loci (0.37 and 0.35, respectively) were much lower than the estimated heterozygosity. The PIC was less than 0.5 in both lines, and average allele number per marker locus was about 3.5. Twenty-five males produced from a cross between these two lines were screened with the DNA marker to select birds with high heterozygosity at marker loci. This experiment demonstrated that the heterozygosity and PIC in commercial broiler lines were low and selection on the birds with high heterozygosity at marker loci can increase informative content in chickens used in the experiments of QTL mapping, thus increasing detection power for QTL mapping.