The physiological effects of breeding lights on broiler and laying hens

Poultry have excellent visual abilities, able to discern light intensity and color. This study used LED lights, a single-wavelength light source, to illuminate broilers and laying hens to investigate the effects of monochromatic light on their growth, development, and production performance. The results showed that in the early growth phase of broilers exposed to green light, the broiler group gained weight faster but had a lower feed-to-grain ratio. Later in the growth phase, the blue light group gained weight significantly but had a lower feed-to-grain ratio. Furthermore, carcass weight, breast muscle weight, thigh weight, calf weight, and evisceration weight were 14.39% to 19.86% higher than those in the other light groups. This indicates that, compared with red and white light, green light promotes growth in the early growth phase, while blue light promotes growth in the later growth phase. Furthermore, using fluorescent light to illuminate broilers, it was found that broilers raised under blue-green light achieved significantly higher weight gain than those raised under red or white light. These results suggest that monochromatic light can significantly affect the growth and development of chickens. Different wavelengths of light can affect the behavior of broiler chickens. For example, broilers raised under red and white light tend to be lethargic, while those raised under blue and green light tend to feed more frequently. This may explain the significantly higher body weight, breast muscle weight, thigh weight, calf weight, and eviscerated weight in broilers raised under blue and green light compared to those raised under red and white light.

The spleen is a large immune organ in animals, containing a large number of lymphocytes and macrophages, and serves as the center of both cellular and humoral immunity. Cellular immunity thickens the periarterial lymphoid sheaths, while humoral immunity results in lymphoid nodules proliferation and a significant increase in plasma cells and macrophages within the splenic cords. Therefore, using HE histological and immunohistochemical staining, we investigated the morphological changes in the spleen and the differences in splenocyte proliferation in laying hens raised under different monochromatic light environments, providing fundamental data for lighting in the poultry industry. The results showed that the diameter of the splenic corpuscles in the red light group increased with age from 20 to 37 weeks, with no significant change from 37 to 52 weeks (P>0.05). Although the area of the lymphoid sheath around the splenic artery decreased at 37 weeks, it rebounded at 52 weeks. These results suggest that red light exposure can improve the immune function of splenocytes in laying hens during the late egg-laying period.