本试验旨在研究活性酵母对脂多糖（LPS）应激黄羽肉鸡肠道健康的影响。选取480羽1日龄黄羽肉公鸡，随机分成6个组，分别为抗生素组（基础饲粮+0.025‰抗生素）、抗生素+LPS组（基础饲粮+0.025‰抗生素，注射LPS）、0.05%活性酵母组（基础饲粮+0.05%活性酵母）、0.05%活性酵母+LPS组（基础饲粮+0.05%活性酵母，注射LPS）、0.50%活性酵母组（基础饲粮+0.50%活性酵母）和0.50%活性酵母+LPS组（基础饲粮+0.50%活性酵母，注射LPS），每组8个重复，每个重复10只鸡。试验期56 d。抗生素+LPS组、0.05%活性酵母+LPS组和0.50%活性酵母+LPS组的试验鸡于21、23、25和27日龄每只鸡肌肉注射2 mL 0.2 mg/mL LPS，其余试验鸡肌肉注射等量生理盐水。于21和27日龄注射LPS或生理盐水后2、4、6、8、10、12和24 h测量试验鸡的直肠温度，并检测27和56日龄试验鸡的肠道细胞凋亡指数以及27、35和56日龄试验鸡的肠道食糜微生物数量和肠道形态结构。结果表明：1）与注射生理盐水相比，LPS刺激显著提高了21日龄注射后2 h和27日龄注射后2和4 h黄羽肉鸡的直肠温度（P<0.05），显著降低了21日龄注射后12 h和27日龄注射后8 h黄羽肉鸡的直肠温度（P<0.05）；饲粮中添加活性酵母对黄羽肉鸡的直肠温度无显著影响（P>0.05）；饲粮中添加活性酵母与肌肉注射LPS对黄羽肉鸡的直肠温度无显著交互作用（P>0.05）。2）与注射生理盐水相比，LPS应激显著提高了27日龄黄羽肉鸡的十二指肠和回肠细胞凋亡指数（P<0.05）；饲粮中添加活性酵母对黄羽肉鸡的肠道细胞凋亡指数无显著影响（P>0.05）；饲粮中添加活性酵母与肌肉注射LPS对黄羽肉鸡的肠道细胞凋亡指数无显著交互作用（P>0.05）。3）与抗生素相比，饲粮中添加0.05%和0.50%的活性酵母显著提高了27、35和56日龄黄羽肉鸡回肠食糜酵母菌数量（P<0.05）；与注射生理盐水相比，LPS应激对黄羽肉鸡回肠和盲肠食糜微生物数量无显著影响（P>0.05）；饲粮中添加活性酵母与肌肉注射LPS对黄羽肉鸡肠道食糜微生物数量无显著交互作用（P>0.05）。4）与抗生素相比，饲粮中添加0.50%活性酵母显著提高了35日龄黄羽肉鸡的空肠绒毛高度（P<0.05）；与注射生理盐水相比，LPS应激显著提高了56日龄黄羽肉鸡的十二指肠隐窝深度（P<0.05）；饲粮中添加活性酵母与肌肉注射LPS对黄羽肉鸡的肠道形态结构无显著交互作用（P>0.05）。综上所述，LPS能成功诱导黄羽肉鸡的免疫应激反应，饲粮中添加活性酵母能够提高黄羽肉鸡肠道绒毛高度和食糜中酵母菌数量，改善肠道黏膜及菌群结构，但肌肉注射LPS与饲粮中添加活性酵母无显著交互作用。

This experiment was conducted to study the effects of active yeast on intestinal health of yellow-feathered broilers challenged by lipopolysaccharide (LPS). Four hundred and eighty one-day-old male yellow-feathered broilers were randomly allotted to six groups with eight replicates per group and ten broilers per replicate. The broilers in antibiotic group were fed with the basal diet supplemented with 0.025‰ antibiotic, that in antibiotic+LPS group were fed with the basal diet supplemented with 0.025‰ antibiotic and injected with LPS, that in 0.05% active yeast group were fed with the basal diet supplemented with 0.05% active yeast, that in 0.05% active yeast+LPS group were fed with the basal diet supplemented with 0.05% active yeast and injected with LPS, that in 0.50% active yeast group were fed with the basal diet supplemented with 0.50% active yeast, and that in 0.50% active yeast+LPS group were fed with the basal diet supplemented with 0.50% active yeast and injected with LPS. The experiment lasted for 56 d. Broilers aged at 21, 23, 25 and 27 days in antibiotic+LPS group, 0.05% active yeast+LPS group and 0.50% active yeast+LPS group were injected intramuscularly with 2 mL 0.2 mg/mL LPS per broiler, and the others were injected intramuscularly with same volume saline. The rectal temperature of broilers aged at 21 and 27 days were measured at 2, 4, 6, 8, 10, 12 and 24 h after the injection of LPS or saline, and the apoptotic index of intestinal cell of broilers aged at 27 and 56 days, microflora number of intestinal chyme and intestinal morphology of broilers aged at 27, 35 and 56 days were detected. The results showed as follows: 1) compared with saline injection, LPS challenged significantly increased the rectal temperature of yellow-feathered broilers at 2 h after injection aged at 21 days and at 2 h and 4 h after injection aged at 27 days (P<0.05), and significantly decreased the rectal temperature of yellow-feathered broilers at 12 h after injection aged at 21 days and at 8 h after injection aged at 27 days (P<0.05). Dietary active yeast had no significant effect on the rectal temperature of yellow-feathered broilers (P>0.05), and dietary active yeast and intramuscular injection of LPS had no significant interaction on the rectal temperature of yellow-feathered broilers (P>0.05). 2) Compared with saline injection, LPS challenged significantly increased the apoptotic index of duodenum and ileum of yellow-feathered broilers aged at 27 days (P<0.05). Dietary active yeast had no significant effect on the apoptotic index of intestinal cell of yellow-feathered broilers (P>0.05), and dietary active yeast and intramuscular injection of LPS had no significant interaction on the apoptotic index of intestinal cell of yellow-feathered broilers (P>0.05). 3) Compared with antibiotic, dietary 0.05% and 0.50% active yeast significantly increased the Saccharomycetes number of ileal chyme of yellow-feathered broilers aged at 27, 35 and 56 days (P<0.05). Compared with saline injection, LPS challenged had no significant effect on the microflora number of ileal and cecal chyme of yellow-feathered broilers (P>0.05). Dietary active yeast and intramuscular injection of LPS had no significant interaction on the microflora number of intestinal chyme of yellow-feathered broilers (P>0.05). 4) Compared with antibiotic, dietary 0.50% active yeast significantly increased the villus height of jejunum of yellow-feathered broilers aged at 35 days (P<0.05). Compared with saline injection, LPS challenged significantly increased the crypt depth of duodenum of yellow-feathered broilers aged at 56 days (P<0.05). Dietary active yeast and intramuscular injection of LPS had no significant interaction on the intestinal morphology of yellow-feathered broilers (P>0.05). In conclusion, the immune stress of yellow-feathered broilers is successfully induced by LPS, and dietary active yeast can increase the intestinal villus height and Saccharomycetes number of chyme, improve the intestinal mucosa and microflora structure of yellow-feathered broilers, but intramuscular injection of LPS and dietary active yeast have no significant interaction.