Effects of B-Wave Ultraviolet Supplementation Using Light-Emitting Diodes on Caged Laying Hens during the Later Phase of the Laying Cycle

SIMPLE SUMMARY: So far, traditional cages are still the dominant housing systems for laying hens all over the world. However, during the later phase of the laying cycle, laying hens in conventional cages are highly susceptible to osteoporosis due to a calcium deficiency, which is accompanied by a decrease in production performance and egg quality, and an increase in mortality. B-wave ultraviolet (UVB) radiation (290–315 nm) can penetrate the skin and converts 7-dehydrocholesterol (7-DHC) to previtamin D(3), which is rapidly converted to vitamin D(3), which promotes the body’s absorption of calcium and phosphorus, as well as bone metabolism. Hence, we hypothesize that UVB exposure using light-emitting diode (LED) lights on laying hens during the later phase of the laying cycle can promote health and welfare of layers. This study aims to improve bone quality and egg quality by utilizing light environment regulation, in order to provide a theoretical basis for the application of UVB-LED lights for laying hens during the later phase of the laying cycle. ABSTRACT: Caged laying hens are prone to calcium deficiencies, resulting in osteoporosis and egg quality deterioration during the later phase of the laying cycle. Fluorescent light and light-emitting diodes (LEDs), which are widely used in poultry houses now, are both deficient in ultraviolet (UV) light, the lack of which is detrimental to chickens’ welfare and health. This study was conducted to investigate the effects of UVB light supplementation using LEDs on the bone traits, blood parameters, laying performance, and egg quality for caged laying hens at 68–75 weeks. In total, 120 Jingfen laying hens were randomly assigned to four different groups, with three replicates in each group (10 hens in each cage as a replicate). UVB-LED lamps installed under the feed troughs were used to provide UVB light (296–316 nm) for the birds in the three treatment groups (1 h, 2 h, and 3 h UVB supplementation per day, respectively), while the control group was not exposed to UVB-LED light. Bone traits, egg quality, and amounts of calcium (Ca), phosphorus (P), 25-hydroxyvitamin D(3) (25(OH)D(3)), 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), and 7-dehydrocholesterol (7-DHC) in both the serum and egg yolks were tested during the experiment. The results demonstrated that UVB-LED exposure significantly increased the bone mineral density (BMD), egg production, and yolk 1,25(OH)(2)D(3) concentrations (p < 0.05), and reduced the content of serum 7-DHC (p < 0.05), especially in the 2 h/day group; however, it did not improve egg quality, vitamin D metabolites, or photoproducts in the serum and yolk 25(OH)(2)D(3) concentrations (p > 0.05). This study concluded that UVB supplementation using LEDs had a positive effect on caged laying hens during the later phase of the laying cycle.