ARS | Publication request: MAPPING QUANTITATIVE TRAIT LOCUS ASSOCIATED WITH RESISTANCE TO AVIAN COCCIDIOSIS AND GROWTH

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2003
Publication Date: September 3, 2003
Citation: Zhu, J.J., Lillehoj, H.S., Allen, P.C., Van Tassell, C.P., Sonstegard, T.S., Cheng, H.H., Pollock, D., Sadjadi, M., Min, W., Emara, M.G. 2003. Mapping quantitative trait locus associated with resistance to avian coccidiosis and growth. Poultry Science 82:9-16.

Interpretive Summary: Avian coccidiosis is an infectious disease caused by several distinct species of Eimeria parasites. The parasites infect the chicken digestive tract, and disease caused by the infection significantly retards growth. The current strategies of disease control are prophylactic medication and vaccination. However, the wide variety of Eimeria strains and continual emergence of drug-resistant strains limit the effectiveness of both methods. An alternative approach to control coccidiosis is to breed chickens resistant to the disease. In this study, ARS scientists collaborated with researchers at Perdue Farms and University of Delaware to map host genes which determine coccidiosis resistance. The results showed that oocyst shedding is the best parameter to measure the status of resistance/susceptibility to coccidiosis and a QTL identical to, or in close proximity with, marker LEI0101 on chromosome 1 is associated with oocyst shedding in Eimeria-infected chickens. This is the first report of an association with a QTL with coccidiosis resistance and will provide important information for the development of DNA marker based strategy for avian coccidiosis for poultry industry.

Technical Abstract: To map quantitative trait loci (QTL) associated with resistance to avian coccidiosis, two commercial broiler lines with different degrees of resistance to the disease were crossed to generate F1 generation that were intercrossed to produce 314 F2 generation offspring. The F2 offspring were inoculated with sporulated oocysts of Eimeria maxima. Five disease-associated traits were measured post-infection. Inter-trait comparisons revealed oocyst shedding to represent the best parameter for evaluating disease resistance/susceptibility. One hundred and nineteen microsatellite markers, covering 80 % of the chicken genome with an average marker interval of 25 cM, were used for genotyping of F1 parents and F2 offspring. Statistical analysis based on data of four families identified a locus on chromosome 1 significantly associated with oocyst shedding (LOD = 3.46). The heritability of oocyst shedding due to the locus was estimated to be 0.54. The genetic mechanism of this locus was mostly additive. The genomic scan also identified three potential growth QTL on Chromosomes 1, 6, and 8. These results will provide the foundation for further investigation to validate the QTL associated with resistance to avian coccidiosis.