Effect of Continuous and Constant Lighting Regimes on Organ Growth in Broilers

This study was undertaken to investigate the effect of gender and lighting regimes on organ growth of broilers. Totally, 312 head one day old chicks (Ross-308) were kept in brooder for the first 7 d, then transferred into the cages, in which the animals were exposed to two lighting regimes [(23L: 1D) and (16L: 8D)]. The samples from sub-groups (gender and lighting groups) were weighed, slaughtered and internal organs were weighed to determine the organ growth on the days zero, 7, 14, 21, 28, 35 and 42 throughout the experiment. To determine the growth rate of organs from the brood to the 42nd d of the experiment, non-parametric Gompertz model was used. Except for the length of the intestine, other organ weights were not affected by the gender of the animals (P 0.05). Lighting regime had significant effect on heart, liver, intestinal weight and intestinal length (P 0.05). The R2 values, calculated by using Gompertz method were between 0.860 and 0.960 and quite high for body, heart, liver, proventriculus, intestinal weight and length of the intestine. Growth rate of the proventriculus was similar in both lighting regimes, while that of other organs was higher in animals exposed to constant (16L: 8D) lighting, than those in continuous (23:L: 1D) lighting. When compared to continuous lighting, the constant regime was concluded to be a superior choice to obtain higher growth rate in broilers.