Selection of broiler chickens for a high and low incidence of tibial dyschondroplasia with observations on spondylolisthesis and twisted legs (perosis).

Radiography was used to select normal birds and affected with tibial dyschondroplasia from a commercial stock of broiler chickens. Birds were selected for three generations and mated like to like in an attempt to establish low and high incidence strains. Incidence of tibial dyschondroplasia in the low incidence strain was reduced to negligible levels while it was increased in the high incidence strain. Incidence of the defect in the high incidence strain could be influenced by diet. Observations during the selection program on the incidence of spondylolisthesis and twisted legs in birds younger than eight weeks of age indicated that these other skeletal defects were unrelated to tibial dyschondroplasia.