effects of lighting programs on immune system and performance of broiler chickens

the aim of this study was to evaluate the effects of three lighting programs on immune system and performance of broiler chickens. a total of 288 seven day-old male broiler chicks (ross-308) were randomly distributed between three treatments. each group was housed in the separated room with eight pen and 12-birds per pen. the management conditions were similar for all treatments throughout the experimental period except lighting programs which were provided as follow: 1) 23 h light (l): 1 h dark (23l:1d), 2) 18 h l: 6 h d (18l:6d) and 3) 14 h l: 10 h d (14l:10d). during the experimental period, feed intake, body weight gain and feed conversion ratio were measured. at the end of 5th-week, two birds from each pen with average weight of pen were selected for determining titer of total immunoglobulin, total complement, total albumin and total protein factors. results did not show any differences between the experimental treatments in feed intake and body weight gain (p>0.05) but fcr was improved in 14l:10d treatment in compare with 23l:1d group (p<0.05). the amount of total immunoglobulin, total protein and total complement factors, were increased in 14l:10d treatment compared to 23l:1d group (p<0.05). it is concluded that long darkness improved feed conversion ratio, innate and humeral immune system responses of birds, however, did not have any negative effect on feed intake and body weight gain.