Effects of lighting programs on immune responses, organ weights, and gait scoring in broiler chickens

Effects of lighting program during production period on organs weight, immune responses, gait scoring, and tonic immobility reaction were evaluated using 900 male day-old broiler chicks (ROSS 308) in three houses. In each house, chicks were randomly allocated to 30 pens of 10 birds each. From day 7 upto 3 days to the end of the production period, three lighting programs including 17L:7D for house 1, 14L:10D for house2, and 12L:12D for house 3 were used. For immune system evaluation SRBC injection and CBH test were used. Blood samples for CBC were collected on day 40. Gait scoring and tonic immobility test were done on day 41. On day 42, 30 birds from each house (one per pen) were selected randomly, euthanized, and carcass and organ weights were recorded. Using 12 hours of darkness, comparing with 7 or 10 hours, decreased gastrointestinal weight while increased testis weight (P<0.05). Increasing the darkness period, increased the eye weight linearly. Incorporation of 10 or 12 hours of darkness decreased PCV percent (P<0.001). Immune system responses were improved by 10 hours of darkness (P<0.05). Application of 10 hours of darkness also improved the gait scoring and tonic immobility values comparing to 2 other darkness periods (P<0.05). Overall, according to the results of this study, using 10 hours of darkness would be beneficial and advisable in broiler production.