Growth and Carcass Quality of Native Chickens Raised under the Natural Day Length and the Photoperiod of Twenty-three Hours a Day

Abstract

The effect of long photoperiod on growth, carcass yield, and carcass composition in native chickens were examined. Two lighting programmes of natural day length (NDL) and photoperiod of 23 hours/day (23L:1D) were set. It was found that the 23L:1D group tended to have better growth than the NDL group. Average body weights of the 23L:1D and NDL groups at 16 weeks of age were 1,508 g and 1,451 g and at 20 weeks of age were 1,803 g and 1,746 g, respectively, while feed conversion ratios of the two groups were not different (P>0.05). Both groups had low mortality rate of only 2-3% with no sign of leg disorder, ascites, and breast blister. In term of carcass yield, males responded to the long photoperiod more than females. As carcass weights of the females of both groups were not different (P>0.05), carcass weights of the male of 23L:1D group were higher than (P<0.05) those of the NDL group. Higher yields were found of those killed at 16 weeks of age in chilled carcass weight (1,606 g, 1,479 g, P<0.05), breast weight (317.9 g, 269.3 g, P<0.05), and drumstick weight (232.5 g, 208.0 g, P<0.05), and of those killed at 20 weeks of age in breast weight (378.4 g, 344.9 g, P<0.05). When compared between age, killing at the older age yielded more meat in term of actual carcass weight (P<0.05) but not in term of percentage of chilled carcass weight (P>0.05) except for the drumstick weight in the male (P<0.05).Chemical compositions of the carcass did not change due to photoperiods (P>0.05) but changed considerably due to ages at killing. In general, meat protein was increased from about 61.0% to 65.2% (P<0.05), meat ash was decreased from about 3.9% to 3.4% (P<0.05), and meat fat showed no noticable change (P>0.05) when compared between killing at 16 and 20 weeks of age.