Effects of intermittent lighting program and light colour on ocular health variables as welfare indicators in broiler chickens.

1. The objective of the present study was to examine the effect of lighting programs and light colour on ocular health variables as welfare indicators in Ross 308 broilers.2. A total of 384, male, one-d-old broiler chickens (Ross 308) were placed in a completely randomised design with a 2 × 2 factorial arrangement of lighting program (continuous or intermittent) and light colour (white and green LED light). Ross 308 broilers under restricted lighting had 18 h of light (18 L:6D), while those under intermittent lighting had cycles of 17 L:3D:1 L:3D throughout the experimental period, which lasted 42 d.3. At the end of the experiment, all eyes of birds ( n  = 96 birds) underwent a complete ophthalmic examination, which included the Schirmer tear test I, intraocular pressure and eye dimensions. In addition, 32 broilers (eight birds per trial groups) aged 42 d underwent ophthalmic examination to include assessment of ocular ultrasound biometry.4. Light colour had a significant influence on the mean intraocular pressure ( p  < 0.001). The Ross 308 broilers kept with intermittent lighting had lower eye weights (2.29 g; p  < 0.05), palpebral fissure length (14.39 mm; p  < 0.01), eye dorsoventral diameter (17.46 mm; p  < 0.05), anteroposterior size (13.70 mm; p  < 0.01) and corneal dorsoventral diameter (7.81 mm; p  < 0.05) compared to those reared under restricted lighting.5. In conclusion, these values for Ross 308 broilers may be applied in poultry ophthalmology to detect early eye disease symptoms and to help the diagnosis of tear disorders that could cause economic losses and welfare issues. Intermittent lighting and green LED light may help reduce eye health problems thus contributing to improved welfare in broilers.