发酵豆粕缓解断奶仔猪腹泻的机理研究

Enterotoxigenic Escherichia coli (ETEC) is a major problem in the swine industry and results in scouring, increased mortality, and poor performance in the period postweaning. The traditional way to control this problem is to include subtherapeutic antibiotics in feed, however, this enhance the risk of antibiotic resistance. Beneficial effects for fermented soybean meal have been reported in improving growth performance, nutrient digestibility and intestinal morphology and reducing diarrhea incidence. On the basis of accumulated relevant work, this project is proposed to study the mechanism of diarrhea control by fermented soybean meal in vivo and in vitro, so that the health and productive performance of weanling piglets could be improved and the antibiotic could be replaced. The effects of fermented soybean meal on diarrhea incidence, microbiota composition and enterotoxin concentration in digesta of weanling piglets after E. coli challenge are investigated. Adhesion of E. coli to the intestinal epithelial cells (IPEC-J2), secretion of E. coli enterotoxin and growth of pathogenic E. coli are studied. Sciences and technologies of animal nutrition, molecular biology, RT-PCR, denaturing gradient gel electrophoresis (DGGE) and phase contrast microscopy is to be adopted.

断奶仔猪腹泻是导致仔猪生产性能下降甚至死亡的主要原因，大肠杆菌是引起断奶仔猪腹泻的主要病原微生物。添加抗生素是最有效的缓解断奶仔猪腹泻的方法，然而抗生素的使用必然会增加病原微生物的耐药性。前期研究表明，用发酵豆粕替代日粮中的豆粕，可以提高断奶仔猪的生长性能及营养物质消化率，减轻肠道损伤，对腹泻有一定的缓解作用。因此、本研究在已有工作积累的基础上提出，以大肠杆菌K88攻毒断奶仔猪为体内模型，研究饲喂发酵豆粕对断奶仔猪生长性能、腹泻率、肠道菌群和食糜中大肠杆菌肠毒素水平的影响；同时以猪肠上皮细胞系IPEC-J2为体外模型，研究发酵豆粕提取物对大肠杆菌K88的生长、肠毒素的分泌和对肠道上皮细胞粘附的影响。根本目的是研究发酵豆粕缓解仔猪腹泻的机理，从而为提高断奶仔猪健康和降低抗生素的用量提供理论依据。

饲料中使用发酵豆粕，可以提高断奶仔猪的生长性能及营养物质消化率，减轻肠道损伤，缓解断奶仔猪腹泻，为了阐明其作用机制，本研究以大肠杆菌K88攻毒断奶仔猪为体内模型，研究饲喂发酵豆粕对断奶仔猪生长性能、腹泻率、肠道菌群和食糜中大肠杆菌肠毒素水平的影响；同时以猪肠上皮细胞系IPEC-J2为体外模型，研究发酵豆粕提取物对大肠杆菌K88的生长、肠毒素的分泌和对肠道上皮细胞粘附的影响。获得了如下研究成果：1）以发酵豆粕代替部分豆粕可提高肠道绒毛高度，上调紧密连接蛋白表达，降低炎症细胞因子的含量，降低Escherichia-Shigella相对丰度，进而缓解腹泻（腹泻率由80.56%降低至61.11%，降低了19.45%），提高仔猪生长性能。2）发酵豆粕与豆粕共得到1450种显著差异代谢物，显著上调的差异代谢物1264种，显著下调的差异代谢物186种。3）发酵豆粕提取物可以抑制大肠杆菌K88的生长，促进猪肠上皮细胞IPEC-J2的增殖，且发酵豆粕提取物可竞争性抑制大肠杆菌K88对IPEC-J2细胞的粘附。4）通过枯草芽孢杆菌和酿酒酵母发酵小麦麸皮制备发酵麸皮多糖，发现微生物发酵可破坏植物细胞壁结构，打开糖苷键，释放如阿魏酸低聚糖、多糖等活性物质，起到抗炎、抗氧化、菌群结构调节等功能。以上研究发现，为进一步分离纯化发酵豆粕中生物活性物质及阐明腹泻缓解机理奠定了基础。

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