Effects of divergent selection for incidence of tibial dyschondroplasia (TD) on purebred and crossbred performance. 2. Processing yield

1. An experiment was conducted to determine the effect of selection for hig h (H) or low (L) incidence of tibial dyschondroplasia for 7 generations on processing performance of broilers. 2. Birds were obtained from diallel matings of the H and L lines (HH, HL, L H, and LL) and a randombred control (CC) line. Birds were reared to 7 weeks of age under standard management conditions. All birds were processed at 7 weeks of age. Body weight at 7 weeks, carcase weight, and carcase part wei ghts were recorded on each bird. 3. An interaction between sire line and dam line was caused by lighter body and carcase weight at 7 weeks of age in HH birds than from the birds of th e other crosses. 4. Birds by L line dams had heavier drumstick weights. The influences of si re line and dam line on weight of total breast muscle were not significant. Thigh weights and Pectoralis minor weights were lighter in HH line birds t han those other matings. 5. Heterosis for body weight and for weights of carcases, drumstick and thi gh was negative. Total breast muscle weight and P. major weight did not sho w significant heterosis. 6. It was concluded that selecting against TD does not reduce processing yi eld of broilers.