A total of 260 one-day-old Arbor Acres male broilers were exposed to red light (RL), green light (GL), blue light (BL), and white light (WL), respectively, by using a light-emitting diode system for 7 wk. There were 5 replicate pens for each light treatment and 13 birds per pen. The effects of monochromatic light on the immune response were studied. The results indicated that proliferation of peripheral blood T lymphocytes in the GL group was significantly increased (by 80.8 and 54.8%) compared with those in the RL and BL groups, respectively, at 21 d of age (P < 0.05). At 49 d of age, however, the proliferation response was significantly increased in the BL group compared with the RL group (26.9%, P< 0.05). Moreover, the GL group showed a significant elevation in the serum anti-Newcastle disease virus level as compared with that of the RL group at 28 d of age (32.9%, P < 0.05). In contrast, no significant difference in serum anti-Newcastle disease virus level was observed among the BL, RL, and WL groups at this age (P > 0.05). By 49 d of age, the antibody titer was higher in the BL group than in the RL group (62.8%, P < 0.05). However, no significant difference in antibody titer was seen among the BL, GL, and WL groups at this age. Interestingly, the BL group showed a 44.0% reduction in the level of serum interleukin-1beta as compared with that in the RL group at 49 d of age (P < 0.05). These results suggest that GL and BL enhance the immune response better than RL, and that BL may play a role in alleviating the stress response in broilers.

Our previous study demonstrated that blue monochromatic light was better to promote the growth and development of broilers than red light. However, consumer research suggests that the eating quality of the meat is more important. The present study was, therefore, designed to further evaluate the effects of various monochromatic lights on the muscle growth and quality properties and antioxidation of meat. A total of 288 newly hatched Arbor Acre male broilers were exposed to blue light (BL), green light (GL), red light (RL), and white light (WL) by a light-emitting diode system for 49 d, respectively. Results showed that the broilers reared under BL significantly increased BW and carcass yield as compared with RL, WL, and GL (P < 0.05), but no statistical difference was found between GL and BL in weight of thigh muscle and carcass yield (P > 0.05). Compared with RL, the muscles of breast and thigh in GL and BL had higher pH, water-holding capacity, and protein content, whereas cooking loss, lightness value, shear value, and fat content were lower (P < 0.05). Moreover, BL significantly elevated superoxide dismutase, glutathione peroxidase, and total antioxidant capability activities and reduced malondialdehyde content both in breast and thigh muscles as compared with RL and WL (P < 0.05), but there was no significant difference in the superoxide dismutase and glutathione peroxidase activities between GL and BL (P > 0.05). These results suggest that BL better improves meat quality of Arbor Acre broilers by elevating antioxidative capacity than does RL.

Our previous studies demonstrated that green and blue monochromatic lights were effective to stimulate immune response of the spleen in broilers. This study was designed to investigate the effects of monochromatic light on both gut mucosal mechanical and immunological barriers. A total of 120 Arbor Acre male broilers on post-hatching day (P) 0 were exposed to red light, green light (GL), blue light (BL), and white light (WL) for 49 d, respectively. As compared with broilers exposed to WL, the broilers exposed to GL showed that the villus height of small intestine was increased by 19.5% (P = 0.0205) and 38.8% (P = 0.0149), the crypt depth of small intestine was decreased by 15.1% (P = 0.0049) and 10.1% (P = 0.0005), and the ratios of villus height to crypt depth were increased by 39.3% (P < 0.0001) and 52.5% (P < 0.0001) at P7 and P21, respectively. Until P49, an increased villus height (33.6%, P = 0.0076), a decreased crypt depth (15.4%, P = 0.0201), and an increased villus height-to-crypt depth ratio (58.5%, P < 0.0001) were observed in the BL group as compared with the WL group. On the other hand, the numbers of intestinal intraepithelial lymphocytes (27.9%, P < 0.0001 and 37.0%, P < 0.0001), goblet cells (GC, 22.1%, P < 0.0001 and 18.1%, P < 0.0001), and IgA(+) cells (14.8%, P = 0.0543 and 47.9%, P = 0.0377) in the small intestine were significantly increased in the GL group as compared with the WL group at P7 and P21, respectively. The numbers of intestinal intraepithelial lymphocytes (36.2%, P < 0.0001), GC (26.5%, P < 0.0001), and IgA(+) cells (68.0%, P = 0.0177) in the BL group were also higher than those in the WL group at P49. These results suggest that both mucosal mechanical and immunological barriers of the small intestine may be improved by rearing broilers under GL at an early age and under BL at an older age.