The incubation conditions (temperature and humidity) have been described previously by Tona et al. [25]. After 21.25 d of incubation, samples of 20 1-d-old highquality chicks selected at random from each tray (20 chicks/group per replicate = 160 chicks in total) were reared for 42 d in a broiler farm to study the relationship between the weights at different stages and the weight at slaughter age. The chicks were weighed at take-off, and each was identified by leg ring number, but from d 7 a wing ring with number was used, and the leg ring was removed