This experiment was designed to study selection for general immunocompetence by using a selection index. A total of 460 chicks from 20 sire families (randomly divided into 2 replicates of 10 sire families each) of a random breeding egglaying chicken line (Ottawa strain 7) were used as the base population. Three in vivo assays (carbon clearance assay, PHA wing web assay and ELISA) were used to evaluate phagocytic activity (PI), cell- mediated response (WI) and antibody production to 2 vaccines, Pasteurella multocida and Mycoplasma qallisepticum (a-PM and a-MG), respectively. Heritabilities of these traits were estimated to be from 0.06 to 0.53. A selection index was constructed with the assumption that genetic correlations between these traits are negligible. The economic value of the traits were calculated to be negatively proportional to their respective heritability estimates on the assumption that equal selection presure would be applied to each trait. After two generations of selection, significant differences were observed between high and low response sublines for anti-MG and WI. Analysis of additional generations will determine the feasibility of multi-trait selection for immunocompetence to increase general disease resistance in poultry.

S. Chang, S. J Lamont

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume XVI. Poultry, fish and horse genetics and breeding, growth and reproduction, immune response and disease resistance., , 58–61, 1990
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