Effects of Light Wavelength on Broiler Performance, Blood Cell Profiles, Stress Levels, and Tibiotarsi Morphology

Lighting influences broiler production, health, and behavior. The objective of this study was to examine the effects of three light wavelengths (White [350-780 nm], Blue [450 nm], and Green [560 nm]) on broiler production, activity, fear, stress, blood cell profiles, and tibiotarsi (tibia) morphology. Day-of-hatch male broiler chicks (N = 600) were housed in pens (N = 12) with one lighting treatment for 42 days. Body weight and feed consumption were recorded on day (D) 0, 14, 28, and 42, and the feed conversion ratio was calculated. The Tonic Immobility test was used to assess the latency (seconds) to right from the testing cradle (D12 and D33). Blood was drawn for leukocyte and plasma corticosterone concentrations (D21 and D41). Accelerometers were attached at 2 and 5 weeks of age to measure activity. On D41, thermal images of the head were taken to measure surface temperatures (eye and beak), the bursa of Fabricius (bursa) was extracted for relative bursa weight, and the right and left tibias were extracted for tibia morphology. After sampling, the remaining broilers were processed. Activity was greatest in Green light at Week 2 (261.17 ± 8.52 m/s², p < 0.0001), and activity was lowest in White light at Week 5 (98.99 ± 8.52 m/s², p < 0.0001). Broilers under Blue light had lower concentrations of lymphocytes (8.62 ± 0.40 × 10³ cells/µL, p = 0.01) and T cells (7.16 ± 0.33 × 10³ cells/µL, p = 0.008) compared to White light. Breast yields were greatest (26.89 ± 0.13%, p = 0.01) in the White treatments compared to Green and Blue treatments. These results suggest that blue light may negatively impact immune health, while green light increases activity, without decreasing production performance, and white light can improve carcass traits. Therefore, lighting color can be strategically used to target welfare or production goals.