Estimates of Heritabilities and Genetic Correlations Between Tibial Dyschondroplasia Expression and Body Weight at Two Ages in Broilers

Genetic variances and covariances were estimated by multiple-trait, derivative-free restricted maximum likelihood (DFREML) using an animal model for tibial dyschondroplasia (TD) expression and body weight at 4 and 7 wk of age. Data were collected from 7,483 broiler progeny obtained from 421 sires and 977 dams as part of a seven-generation selection experiment for high, and low TD expression, along with a randomly selected control line. Heritability estimates for TD expression and body weight at 7 wk were 0.42 and 0.50, respectively, larger than the corresponding estimates of 0.37 and 0.42 at 4 wk of age. Genetic correlations of TD