عنوان مقاله [English]
This experiment subjected to investigate the effect of different light programs on growth performance, the immune system and internal organs of the broiler chicks. A total of 300 one day-old male broiler chicks (Ross-308) were randomly distributed between three treatments with a similar average weight. Each group was housed in the separated room with five pen and 20-birds per pen.The management conditions were similar for all treatments throughout the experimental period except lighting programs which from 8 to the 42 day were provided as follow: 1) 23 h light (L): 1 h dark (23L:1D), 2) 16 h L: 8 h D (18L:6D) and 3) 12 h L: 12 h D (12L:12D). At 35day-old, 0.2 mL of SRBC was injected intravenously into the chicks and at the 42 day-old, 4 chicks were randomly selected from each replicate. Anti-SRBC antibody titers were determined using a heamagglutination technique. Then Chicks were slaughtered and their bursa of fabricus, spleens, liver, heart, crops, gizzard and jejunum weighted and alsolength of jejunum were measured. The Anti-SRBC titer was the lowest with 23L:1D and the highest in the birds of 12L:12D treatments respectively (p < 0.01). The lowest weights of internal organelles were in 23L:1D and the highest in 12L:12D treatments.The weight gain and feed conversion ratio between the treatments was significantly different in all the periods and improved with more dark hours (p < 0.05). It is concluded that lighting program with long darkness improved growth and immune indices in broilers.