COMPARISON OF OUTBRED LINES OF CHICKENS FOR RESISTANCE TO EXPERIMENTAL-INFECTION WITH COCCIDIOSIS (EIMERIA-TENELLA)

Coccidiosis causes dramatic economic birds to this parasitic disease r epresents an attractive alternative. An experiment was run in order to identify lines of chickens resistant and susceptible to coccidiosis a s a tool to search for genetic markers of resistance. Five outbred Lin es were used: two Egyptian lines (Mandarah and Fayoumi), a Rhode Islan d Red line, and two White Leghorn lines (WLB21 and WLDW). The WLDW lin e segregated for three MHC haplotypes, B-15, B-19, and B-21, and for t he sex-linked dwarf gene, DW. Chicks were challenged at 4 wk of age wi th a high dose of Eimeria tenella (150,000 oocysts) and slaughtered 8 d postinoculation. Innate resistance was assessed individually by meas ures of lesion score, mortality, and body weight gain at slaughter, an d plasma coloration 4 d postinoculation. Large differences in resistan ce to E. tenella were observed between lines. The Fayoumi line appeare d clearly as the most resistant line, showing no mortality, less sever e lesions than other lines, and a 30% reduction of growth as compared to control birds. The WLDW line was the most susceptible, with 27% mor tality and a 85% reduction in growth. No major effect of MHC or dwarfi sm on resistance to E. tenella was found.