Blood parameters of dwarf and normal pullets from growth selected lines before and after Escherichia coli challenge

Two experiments were conducted to study the hematological differences and the effect of challenge with Escherichia coli on the hemopoietic system among dwarfs and their normal sisters in lines selected for high and low juvenile body weight. Erythrocyte counts, packed cell volumes, and hemoglobin concentrations were significantly higher to dwarf than for normal pullets, while no such differences were noted for mean corpuscular volume, mean corpuscular hemoglobin and hemoglobin concentration. Dwarfs had a significantly lower erythrocyte sedimentation rate than normal pullets. The effect of challenge with E. coli was evident in all the groups. Body weight decreased and leucocyte counts increased significantly. Lymphopenia, accompanied by heterophilia and a consequent increase in H:L ratio was the conspicuous effect of the challenge with E. coli indicating a polymorphonuclear response. Forty-eight hours after challenge the differential response of lines and genotypes to heterophilia was uniform. The hematological data suggest that the dw gene may not contribute to resistance to bacterial diseases. Mortality and autopsy lesions data indicate that the dw gene had a deleterious effect in the low weight but not in the high weight line, suggesting that its influence on the traits measured is dependent upon the genetic background of the population.