Optimization Of Multi-strain Co-fermented Feed And Its Effect On Anti-salmonella Infection In Broilers

Multi-strain co-fermented feed is rich in probiotics and has a variety of beneficial metabolites.Research and practice have proven that it can effectively improve animal's health level.At present,improving the fermentation effect of fermented feed has become a research hotspot in related fields.In addition,the study confirmed that multi-strain co-fermented feed can effectively improve the animal's intestinal barrier function,and its probiotics,short-chain fatty acids(SCFA),etc.can effectively resist salmonella infection,so we speculated that multi-strain co-fermented feed has the ability of resisting Salmonella infection.Therefor,we explored the effects of acid protease and non-starch-polysaccharides enzyme on the multi-strain co-fermented feed,and selected the optimal amount.Based on this,we analyzed the changes of the functional ingredients and vitro antibacterial properties during the fermentation,and then explored the influence of multi-strain co-fermented feed on the ability of helping broiler to resist salmonella infection so that we can provide an idea and theoretical basis for the better application of multi-strain co-fermented feed.The main research contents were as follows:Fistly,Different dosages of acid protease and NSP enzyme were added when we preparaed the multi-strain co-fermented feed,then we evaluated the effects of acid protease and NSP enzyme from three aspects which are total bacterial count,metabolites and vitro antioxidant activity,and found the best added amount.The results showed that acid protease and NSP enzyme can significantly improve the fermentation effect of probiotic mixed fermented feed.The optimal addition amount of acid protease was 0.4 g/kg,and the optimal addition amount of NSP enzyme was 0.15 g/kg.The effect of acid protease was better than NSP enzyme.Therefore 0.4 g/kg of acid protease was added for subsequent experiments.Secondly,we analyzed the changes of the functional ingredients and vitro antibacterial propertiesd during fermentation.The results showed that after fermentation,the pH decreased significantly,and the total number of probiotic,the content of total acid,amino acid nitrogen,short-chain fatty acids,and small peptide increased significantly,the antioxidant capacity in vitro enhanced obviously,and fermentation produced Nisin Z and made the feed showed antibacterial capability,which showed an upward trend with the extension of fermentation time.Finally,we investigated the effect of multi-strain co-fermented feed on anti-Salmonella infection in broilers:50 one-day-old broilers were randomly divided into 5 groups:normal group(basal diet+10%unfermented feed);model group(basal diet+10%unfermented feed);antibiotic group(basal diet+10%unfermented feed+20 mg/kg colistin sulfate);5%fermented group(basal diet+5%fermented feed+5%unfermented feed);10%fermented group(basal diet+10%fermented feed).Oral administration of 400?L of Salmonella(10~9 CFU/mL)for two days except the normal group when the broilers were 13-day-old,the normal group was given equal volume of sterile water.We observed obvious diarrhea in model group.The broilers were slaughtered at the age of 15 days.We evaluated the effect of multi-strain co-fermented feed on the broilers that challenged with Salmonella from three aspects which are inflammation,oxidative stress,and intestinal barrier function.The results showed that,(1)Multi-strain co-fermented feed and colistin sulfate can reduce the level and mRNA expression of pro-inflammatory cytokine(IL-1?,IL-6,TNF-?)by inhibiting the activation of TLR4/MyD88/NF-?B signaling pathway that caused by Salmonella infection.The level and mRNA expression of anti-inflammatory cytokines(IL-4,IL-10)in 5%fermented group and10%fermented group were significantly higher than other three groups,indicating that multi-strain co-fermented feed can inhibit intestinal inflammation.The MPO activity in the 10%fermented group and antibiotic group was significantly lower than the model group.In summary,the multi-strain co-fermented feed can reduce the inflammatory response that caused by Salmonella infection.Overall,the inflammation improvement of the 10%fermented group was close to the antibiotic group and better than the 5%fermented group.(2)Salmonella infection caused the significantly decrease of T-AOC,antioxidant enzymes(T-SOD,CAT?GSH-Px)activity and malondialdehyde(MDA)content in serum and colon,multi-strain co-fermented feed and colistin sulfate can improve these situation,Overall,the antioxidant indexes in 5%fermented group and 10%fermented group were better than the antibiotic group.(3)Salmonella infection caused the impaired colon morphology,led significantly increase of LPS and D-LA content in serum,caused significantly decrease of SIgA content in Colon mucosa,and low level mRNA expression of tight junction protein(ZO-1?Claudin-1?Occludin),MUC2,and caused unusual high m RNA expression of?-defensin(AVBD-6,AVBD-9),indicating that Salmonella infection destroyed the intestinal barrier.Multi-strain co-fermented feed and colistin sulfate can adjust these abnormal phenomenon to reduce the damage that caused by Salmonella infection.Overall,the intestinal barrier function of the 10%fermented group was similar to that of the antibiotic group and superior to the 5%fermented group.In conclusion,acid protease and NSP enzyme can improve the fermentation effect of multi-strain co-fermented feed.The optimal amount of acid protease is 0.4 g/kg.The optimal amount of NSP enzyme is 0.15 g/kg.The effect of acid protease is better than NSP enzyme;Fermentation can increase functional ingredients,and the antibacterial performance is shown after fermentation;Multi-strain co-fermented feed can ameliorate inflammation,oxidative stress and intestinal barrier damage that caused by Salmonella infection,the effect of 10%fermented feed is better than 5%fermented feed,and close to 20 mg/kg colistin sulfate.