Abstract:

 In order to study the effect of the Bacillus probiotics on blood cells and tissue structure of broilers, 480 newly hatched AA chicken were randomly divided into control group, antibiotic group, experiment Ⅰ and Ⅱ groups. The control group was fed with basal diet, and the antibiotic group was fed with 50 mg·kg^－1 chlortetracycline in the basal diet, and the experimental Ⅰ and Ⅱ groups were respectively fed with 200 and 400 mg·kg^－1 the Bacillus probiotics in the basal diet for 42 days. The results showed: compared with the control group, the quantity of red cells and the ratio of basophilic granulocytes and monocytes were significantly increased in 21- and 42-day- old broilers (P<0.05), and the weight and organ index of thymus and bursal of the 42-day-old broilers were respectively increased by 46.60% and 38.23%, 66.67% and 47.62% (P<0.05); The weight and organ index of bursal were significantly increased by 35.40% and 36.92%, 88.03% and 153.97% in the 21- and 42-day-old broilers (P<0.05), and the weight and organ index of thymus of the 42-day-old broilers were significantly increased by 46.27% and 28.13% in experiment Ⅰ group (P<0.05); the quantity of white cells was obviously decreased, and the weight and organ index of spleen were also obviously decreased in the antibiotic group at the 42 d (P<0.05). Compared the tissue structure of immune organs in experiment Ⅰand Ⅱ group with the control group, the quantity of spleen node were increased, and periarterial lymphatic sheath were thickened; the thymic cortex were also thickened, and the quantity of thymic corpuscle were decreased; the bursal node were greatened with tightly rank lymphocytes, and which change were more obvious in the experiment Ⅰthan the experiment Ⅱ group. But the tissue structure of immune organs showed different degree atrophy in the antibiotic group. The results suggested that addition of 200 mg·kg^－1 the Bacillus probiotics are better to improve development of immune organs and strengthen immune function than that of 400 mg·kg^－1 the Bacillus probiotics.