EFFECT OF SELECTION FOR HIGH OR LOW INCIDENCE OF TIBIAL DYSCHONDROPLASIA FOR 7 GENERATIONS ON LIVE PERFORMANCE

An experiment was conducted to determine the effect of divergent selec tion for tibial dyschondroplasia (TD) on live performance of broilers. Broilers used in the experiment were produced from the parental lines select-ed for high (H) and low (L) incidence of TD and a randombred c ontrol (C) line. Diallel crosses were made between H and L lines. The offspring produced were HH, HL, LH, LL, and CC, where the first letter refers to sire line and the second letter refers to dam line. Body we ights, average daily body weight gains, and exponential growth rates w ere determined at weekly intervals. The incidence of TD was recorded a t 4 and 7 wk of age. There was no difference among body weights of lin es up to 5 wk of age. Sire lines influenced body weights of birds from 5 to 7 wk of age. A significant interaction between sire and dam line s for body weight was the result of decreased body weights of birds in the HH line from 5 to 6 wk of age. There was a similar interaction fo r body weight gain, which resulted in a slower growth rate of birds in the HH line from 3 to 5 wk of age. Tibial dyschondroplasia incidence was 84.1 and 92.0% in the HH line, 5.6 and 5.4% in the LL line, and 7. 0 and 13.2% in the CC line at 4 and 7 wk of age, respectively. It was suggested that genetic predisposition for TD was independent of body w eight.