Effects Of Yeast Fermentation Products On Growth Performance And Intestinal Health Of Weaned Piglets Challenged With Salmonella Typhimurium And Its Mechanism

Since the early 1990s,antibiotics as growth promoter have been widely used in animal husbandry in China.Unabsorbed antibiotics are excreted in urine or feces and eventually enter the human body through the food chain,leading to the increase of drug resistance in humans.Therefore,looking for environmental protection feed additives has become an urgent priority.Yeast fermentation products of technological fermentation,which are rich in nutrients and metabolites can promote animal growth and enhance animal immunity,and will not result in drug resistance.Studies have shown that yeast fermentation products can promote gut health.However,the role mechanism by which yeast fermentation products alleviate intestinal environment disturbance and intestinal inflammation induced by pathogenic bacteria is still unknown.Therefore,Salmonella typhimurium was selected to treat piglets to simulate intestinal inflammation to explore the effects of yeast fermentation products on intestinal inflammation and its mechanism.1 Effects of supplementation yeast fermentation products on growth performance and blood parameters of piglets challenged with Salmonella typhimuriumA total of 24 male piglets（Duroc×Yorkshire×Landrace）were randomly allotted to four dietary treatments included:（1）Control group（Con）;（2）Salmonella typhimurium group（ST）;（3）Salmonella typhimurium+low-dose yeast fermentation products group（0.2%YFP）;（4）Salmonella typhimurium+high-dose yeast fermentation products（0.4%YFP）.The experiment lasted for 35 days.After 21 days experimental diets feeding,the piglets of the last three groups orally inoculated with 5 m L suspension containing 10⁹ CFU/m L of Salmonella typhimurium.A week later,the second challenge was performed the same as the first.All piglets were slaughter and sampling at 35^th day.Blood was collected when sampling.Body temperature of piglets was measured at pre-and post challenge.Body weight and feed consumption of per piglet was recorded every day of the experiment.The results showed that there were no any significant differences in the average daily gain（ADG）,average daily food intake（ADFI）and the feed to meat ratio（F:G）in the condition of normal feed compared with the Con.Dietary supplemented with 0.4%YFP significantly increased ADG（P<0.05）,and also significantly reduce F:G（P<0.05）at post-challenged with Salmonella typhimurium.The concentrations of CORT,T4,ALT,AST,LDH,CHOL,LDLC,IL-1βand IL-6 in plasma were significantly decreased with the supplementation with 0.4%YFP post-challenge Salmonella typhimurium（P<0.05）.These results indicated that dietary supplementation with yeast fermentation products can significantly improve the growth performance and immunity of piglets after challenged with Salmonella typhimurium.2 Effects of supplementation yeast fermentation products on duodenum health of piglets challenged with Salmonella typhimuriumDuodenum at the same location（about 10 cm from the pylorus）was collected to observe of duodenal morphology.Besides,the same location（about 15 cm from the pylorus）was collected to detect the expression of related genes and proteins.The results showed that dietary supplementation with 0.2%and 0.4%YFP could increase the duodenum villus height and the ratio of villus height to crypt depth（P<0.05）.Dietary supplementation with 0.4%YFP could significantly increase the expression of tight junction protein Occludin in duodenum（P<0.05）.Dietary supplementation with 0.4%YFP significantly affected the expression of apoptosis-related molecules in duodenal epithelial cells（P<0.05）.Dietary supplementation with 0.4%YFP significantly decreased the expressions of pro-inflammatory cytokines and TLR4 signaling pathway related molecules in the duodenum（P<0.05）and significantly increased the expression of anti-inflammatory cytokine（P<0.05）.Dietary supplementation with 0.2%and 0.4%YFP significantly reduced the phosphorylation level of MAPK related proteins and inhibited the activation of MAPK pathway（P<0.05）.These results indicated that dietary supplementation with yeast fermentation products can alleviate intestinal inflammation,reduce intestinal epithelial cell apoptosis,keep intestinal integrity and mucosal barrier function,and maintain intestinal health.The 0.4%group showed better growth-promoting and inflammation-reducing effects.3 Effects of supplementation yeast fermentation products on colonic microbiota and colon inflammation of piglets challenged with Salmonella typhimuriumAccording to the previous results,we only used the dose of 0.4%in this study.Colon at the same location（about 10 cm of the distal colon）was collected to observe colon morphology.Besides,the same location（about 15 cm of the distal colon）and the contents were collected to detect the expression of related genes and proteins.Colon contents were used for 16S r DNA to observe the changes of colonic bacteria composition and to detect the concentrations of short chain fatty acids.The results showed that dietary supplementation with YFP increased the number of goblet cells,reduced inflammatory cell infiltration and integrated the crypt in the colon.Dietary supplementation with YFP significantly decreased the expressions of pro-inflammatory cytokines IL-1β,IL-6,IL-18,TNFαand IFNγin colon（P<0.05）.Dietary supplementation with YFP significantly increased the expression of tight junction proteins ZO-1 and Occludin in colon（P<0.05）.Dietary supplementation with YFP significantly increased the numbers of bacteria producing short-chain fatty acid,thus increasing the concentrations of short-chain fatty acids（SCFAs）.SCFAs activated PPARγ,then inhibited the activity of Nos2,and significantly reduced the content of nitrate in the enteric cavity（P<0.05）.In addition,dietary supplementation with YFP significantly reduced the expression of anaerobic glycolysis related genes in colonic epithelial cells,which ultimately significantly reduced the expansion of Proteobacteria（P<0.05）.These results suggest that the metabolic pattern of colon epithelial cells is biased towards anaerobic glycolysis in inflammatory bowel disease and the by-products such as nitrate and lactic acid entered into the colon lumen,increasing the number of facultative anaerobe.Supplemented yeast fermentation products normalized the metabolism of colonic epithelial cells,thereby reducing the proliferation of facultative anaerobes such as Proteobacteria.