during the period from 22/9-10/11/2019 (for a period of 49 days). This study aims to demonstrate the effect of different systems of lighting on production performance, leg abnormalities, total mortality rate and some microbial traits in broiler chickens. 300 unsexed Ross308 chicks were used in the study at one day age with an average initial weight of 37.5 g. They were randomly distributed to five experimental treatments with three replicates for each treatment. Chicks were fed on starter diet for the first three weeks of age, and finisher diets for the fourth, fifth, sixth and seventh weeks of bird age. All birds switched to continuous lighting (24 hours light) during the first week of age. On the eighth day, the experiment was divided into five treatment ,The first program was Tc (control) 24 hours of light, the second T1:18 hours of light: 6 hours of darkness, and the third T2: 19 hours of light: 2 hours of darkness: 1 hour of light: 2 hours of darkness and the fourth T3:17 hours of light: 3 hours of darkness :1 hour of light: 3 hours of darkness, 5 hours of darkness, T4: 15 hours of light: 4 hours of darkness: 1 hour of light: 4 hours of darkness. (Up to the age of 6 weeks) and at the seventh week, all birds were exposed to continuous lighting for 24 hours of light. The results indicated that there were no significant differences in dressing yield with out and with edible organs at 6,7 weeks. While significant differences (P <0.05) were observed in the relative weight of the thighs and wings parts in the treatment T3 compared with the control Tc treatment at the seventh week of age and a high significant superiority (P <0.01) for the treatment T3 in the relative weight of neck cutter for the same age, Whereas, the control Tc treatment was significantly superior (P <0.05) in the relative weight of the liver compared to the T1 treatment at the sixth week of age. Treatment T2 (P<0.01 and P <0.05) was significantly compared with all trial treatments in pH value in crop, duodenum and ileum at 7 weeks of age. A significant increase (P <0.05) was observed in the T2 treatment compared to the control treatment in the relative weight of thymus gland at the seventh week of age, and highly significant (P <0.01) in the T3 treatment compared to the control treatment in the antibodies directed against Newcastle disease. Conclusion: It is concluded from this study that intermittent lighting programs Improved immune system function and reinforcement Production of antibodies against Newcastle disease and improved pH value of the digestive system.

during the period from 22/9-10/11/2019 (for a period of 49 days). This study aims to demonstrate the effect of different systems of lighting on production performance, leg abnormalities, total mortality rate and some microbial traits in broiler chickens. 300 un-sexed Ross308 chicks were used in the study with an average initial weight of 37.5 g. They were randomly distributed to five experimental treatments with three replicates for each treatment. Chicks were fed on starter diet for the first three weeks of age, and finisher diets for the fourth, fifth, sixth and seventh weeks of bird age. All birds switched to continuous lighting (24 hours light) during the first week of age. On the eighth day, the experiment was divided into five treatment, The first program was Tc (control) 24 hours of light, the second T1: 18 hours of light: 6 hours of darkness, and the third T2: 19 hours of light: 2 hours of darkness: 1 hour of light: 2 hours of darkness and the fourth T3: 17 hours of light: 3 hours of darkness : 1 hour of light: 3 hours of darkness, 5 hours of darkness, T4: 15 hours of light: 4 hours of darkness: 1 hour of light: 4 hours of darkness. (Up to the age of 6 weeks) and at the seventh week, all birds were exposed to continuous lighting for 24 hours of light. The results indicated that there were no significant differences in body weight, weight gain, feed consumption, feed conversion ratio. While, significant differences were observed in the percentage of leg abnormalities and total mortality, where the treatment of control Tc was highly significant (P <0.01) in the incidence of leg abnormalities and the percentage of total mortality rate due to metabolic diseases(Ascites) and sudden death syndrome compared with all intermittent lighting programs. As it can be seen from the results, there was a high significant increase (P <0.01) in the number of Lactobacilli bacteria in intermittent lighting treatments compared to the control treatment Tc in the crop, duodenum and the jejunum. The number of E.coli bacteria increased significantly (P<0.01,0.05)in the control treatment Tc compared with the intermittent light treatments in same character(crop, duodenum and the jejunum). conclusion: It is concluded from this study that intermittent lighting programs reduced the incidence of leg abnormalities, as well as reduced the mortality resulting from metabolic diseases such as (Ascites) and sudden death syndrome, and improved the microbial characteristics of the digestive system without affecting production performance.