RESISTANCE OF CHICKENS TO AN OUTBREAK OF NECROTIC ENTERITIS AS INFLUENCED BY MAJOR HISTOCOMPATIBILITY GENOTYPE AND BACKGROUND GENOME

An outbreak of necrotic enteritis occurred in chickens that were B-13B -13 or B21B21 at the MHC in sublines of lines selected for high (HA) a nd low (LA) antibody response to sheep erythrocytes. Percentage mortal ity and hen-day egg production, although similar for both background g enomes, were different for MHC genotypes. Mortality was 6% for B21B21 and 15% for B-13B-13 types. Although hen-day egg production for both t ypes declined from about 76 to 50%, the decrease occurred earlier but recovery of survivors was faster in B-13B-13 than in B21B21 pullets.