Effects of Green or a Combination of Green and Blue Monochromatic Light on Growth, Carcass Yield, the Heterophil- to-Lymphocyte Ratio and Eye Morphology of Thai Indigenous Chickens

In total, 240 one day old Thai-native chickens (Gallus domesticus) were housed in floor pens, located in a light-proof shed and exposed to one of the following lighting treatments: 1) white fluorescent light throughout the 16 wk of the experimental period (WF), 2) green light provided by a light emitting diode (LED) throughout the experimental period (GLED) and 3) green LED light for the first 3 wk then switching to blue LED light provided for the remaining 13 wk (G-BLED). All treatments were provided with a daily light:dark photoperiod of 23:1 hr over the 16 wk growing period, and there were four replicate pens of 20 straight-run chickens for each treatment. Live performance and the mortality rate were recorded during the experimental period. Feed and water were available at all times. Cumulative feed consumption, feed conversion ratios and mortality rates were similar among the treatment groups. At 6 wk of age, the body weight of the GLED birds was significantly heavier than that of the WF birds, whereas the G-BLED birds had an intermediate value compared with those of the other two treatment groups. Whole carcass and carcass yield characteristics of male chickens processed at age 16 wk were similar for all light treatments, except for relative weights, expressed as percentages of body weight and lean carcass weight, of the liver where the liver relative weights of the WF treatment group were significantly greater than those of the GLED treatment group. There were no significant differences among the treatment groups for weights of the spleen, thymus and bursa of Fabricius. Neither the hematocrit value nor eye morphology of the male birds measured at age 16 wk were influenced by the light treatments. However, the WF birds had a higher heterophil-to-lymphocyte ratio (P < 0.05) compared with the GLED and G-BLED birds. It was concluded that green or blue light has little effect on growth stimulation and the carcass yield of Thai-native chickens without any deleterious effect on eye morphology. The results suggested that the light spectra reduced aggression and activity in the birds. Nevertheless, an additional effect of light intensity may exist and should not be excluded. The LED lighting regimens could be beneficial for energy conservation, the reduction of rearing costs and the improvement of the well-being of the birds.