Resistance, susceptibility, and immunity to cecal coccidiosis: Effects of B complex and alloantigen system L


This study examined alloantigen system L effects on resistance to initial infection and acquired immunity to Eimeria tenella infection in three B complex genotypes. Experimental progeny segregating for B and L genotypes were produced from pedigree matings of (BB5)-B-2 (LL2)-L-1 sires and dams. Chicks were weighed and inoculated with 30,000 E. tenella oocysts at 6 wk of age to evaluate resistance in four trials (n = 262). Immunity was studied in four additional trials (n = 244) by immunizing progeny with 500 E. tenella oocysts per day for 5 d beginning at 5 wk of age. Two weeks after the last immunization dose, the birds were weighed and challenged with 30,000 E. tenella oocysts. All birds were weighed again and scored for cecal lesion 6 d after the 30,000 oocyst dose challenge. Weight gain and cecal lesion scores were evaluated by ANOVA. Major histocompatibility (B) complex genotypes (BB2)-B-2 and (BB5)-B-5 did not affect resistance to initial challenge with E. tenella based on lesion score and weight gain. However, after immunization, the (BB5)-B-5 and (BB5)-B-2 genotypes had significantly lower cecal scores than the (BB2)-B-2 genotype when the birds were rechallenged. Weight gain was not affected among immunized birds. No significant L system effects with or without immunization were detected. These results are consistent with previous research demonstrating B complex effects on immunity to cecal coccidiosis.

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Poultry science


Poultry Science Association

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