Effects of blue-green LED lights with two perceived illuminance (human and poultry) on immune performance and skeletal development of layer chickens

Light is one of the essential environmental factors in the production process of laying hens, which can directly affect their behavior, growth and development, and production performance. The spectral sensitivity of humans is different from that of poultry, and the perceived illuminance units of human and poultry are lux and clux, respectively. If the light management of laying hen production is carried out according to human perceived illuminance, the growth and development of laying hens during pullet rearing may be adversely affected due to the discomfort of the perceived illuminance. Preliminary research has found that blue-green LED light can improve the immune function of laying hens during the brooding and rearing periods. However, the differences of the effects caused by blue-green light on the immune performance and bone development of laying hens during pullet rearing are still unclear for the 2 spectral sensitivities. A total of 120 Jinghong layer chickens were raised from 1 d to 13 wk of age in one of three groups with a white LED light (light intensity unit lux, WL) group, a blue-green LED light (light intensity unit lux, HBGL) group, and blue-green LED light (light intensity unit clux, PBGL) group, and unlimited feed and water were provided during the whole experiment. At 7 and 13 wk of age, the immune performance, bone parameters, and related gene expression were investigated. The results showed that compared with the WL groups, HBGL and PBGL increased the immunoglobulin A (IgA) content at 13 wk of age and the IgM content at 7 wk of age (P < 0.05). The bone mineral density (BMD) at 7 and 13 wk of age and tibial strength (TS) at 13 wk of age of the pullets in the WL group were significantly higher than those in the HBGL and PBGL group (P < 0.05). Osteoclastogenesis inhibitory factor gene (OPG mRNA) expression was increased in the layer chickens at the age of 7 and 13 wk for the WL group (P < 0.05). Compared with the WL group and PBGL group, the melanopsin gene (OPN4 mRNA) transcription level of hypothalamus and pineal gland of the chickens under HBGL significantly increased at 7 and 13 wk of age (P < 0.05). In conclusion, blue-green LED light with two perceived illuminance (human and poultry) can increase the Ig content and the immune performance of layer chickens, and blue-green LED light (light intensity unit lux) can promote the expression of OPN4 gene in the hypothalamus and pineal gland. In addition, white LED light can enhance bone quality by increasing tibia OPG gene expression.