| The purpose of this experiment was to observe the growth performance of ducklings,determine the content of inflammatory factors in serum and intestine,pancreatic digestive enzyme index,abundance and structure of intestinal flora,and the expression of key proteins in the NLRP3/NF-κB/TLR5 signaling pathway.Healthy ducks were selected,and their intestinal contents were taken after being killed.And then probiotics were isolated,identified and screened.Finally,the screened bacillus and lactic acid bacteria were expanded to prepare the compound probiotics used in the experiment.One hundred and twenty ten-day-old Tianfu Ma ducks were randomly divided into 6 groups with 4 replicates in each group and 5 ducks in each replicate.They were divided into control group,model group,natural recovery group,probiotics prevention group,probiotics treatment group and antibiotics treatment group,respectively.The experimental period was 14 days.On the 0th day of the experiment,the prevention group was fed with basal diet and probiotics(10~7cfu/animal),and the other groups were fed with basal diet.On the 5th day of the experiment,except for the control group,the other groups were challenged by intraperitoneal injection of E.coli(1.9×10~7cfu/animal).On the 7th day,probiotics(10~7cfu/animal)were added to the probiotic treatment group and antibiotics(0.1g/kg diet)were added to the antibiotic treatment group after the onset of the infection for 7 days.On the14th day of the experiment,samples were collected and tested by ELISA,high-throughput sequencing,q PCR and Western blot.The results showed that:(1)Effects of duck-derived probiotics on digestive enzymes in pancreas of ducks challenged with Escherichia coli.Compared with the control group,amylase and protease contents in pancreas of model group,natural recovery group,probiotic prevention group,probiotic treatment group and antibiotic treatment group were significantly decreased(p<0.01),and lipase contents in pancreas of model group,natural recovery group,probiotic treatment group and antibiotic treatment group were significantly decreased(p<0.01),but there was no significant difference in pancreatic lipase content in probiotics prevention group(p>0.05).(2)Effects of duck-derived probiotics on growth performance of ducks challenged with Escherichia coli.On the 14th day of the experiment,compared with the control group,the feed to meat ratio of probiotics prevention group,probiotics treatment group and antibiotic treatment group had no significant difference(p>0.05),but the feed to meat ratio of natural recovery group had significant difference(p<0.05).The body weight and feed intake of probiotics prevention group and control group were significantly higher than those of natural recovery group,probiotics treatment group and antibiotic treatment group(p<0.05).The mortality of natural recovery group was significantly higher than that of control group,probiotic prevention group,probiotic treatment group and antibiotic treatment group.(3)Effects of duck-derived probiotics on the serum inflammatory factors of ducks challenged by E.coli.After the challenge,the serum IL-1β,IL-6,IL-8,and TNF-αcontents of ducks in the model group,probiotic prevention group,natural recovery group,probiotic treatment group,and antibiotic treatment group were significantly higher than those in the control group(p<0.05).On the 14th day of the experiment,compared with the control group,there was no significant difference in the contents of IL-1βand IL-6 between the probiotic prevention group and the antibiotic treatment group(p>0.05);the contents of IL-1β,IL-6,IL-8.TNF-αin the serum of ducks in the natural recovery group were significantly higher than those in the control group(p<0.05).(4)Effects of duck-derived probiotics on intestinal microflora of ducks challenged with Escherichia coli.From the perspective of phylum,Firmicutes decreased and Proteus increased in the model group and natural recovery group.Theα-indexes of model group and natural recovery group were significantly lower than those of other groups.The species diversity of probiotics prevention group was higher than that of probiotics treatment group.(5)Effects of duck-derived probiotics on NLRP3/NF-κB/TRL5 receptor protein in the intestine of ducklings.Compared with the control group,the intestinal IL-8,IL-6,IL-1β,and TNF-αcontents in the probiotic prevention group,probiotic treatment group,and antibiotic treatment group increased(p<0.01).The contents of IL-6,IL-1β,and TNF-αin the natural recovery group were significantly higher than those in the probiotic prevention group(0.01<p<0.05),and the contents of intestinal IL-8 were significantly higher than those in the probiotic prevention group(p<0.01).The contents of intestinal IL-6,TNF-αand IL-1βin the the antibiotic treatment group were not significant compared with the probiotic prevention group and the probiotic treatment group(p>0.05).The m RNA relative expression and protein expression of TLR5,NLRP3,Caspase1 and NF-κB protein in the model and natural recovery group were significantly higher than those of the control group(p<0.01),but the m RNA relative expression and protein expression of TLR5 and NF-κB in the model group and the natural recovery group were not significantly different(p>0.05).The m RNA relative expression and protein expression of TLR5,NLRP3,Caspase1 and NF-κB in the probiotic prevention group,probiotic treatment group and antibiotic treatment group were significantly lower than those of the model group(p<0.01).In conclusion,probiotics can reduce the mortality of E.coli infected ducks,maintain the diversity and structural stability of intestinal flora of E.coli infected ducks,and reduce the protein expression levels and m RNA relative expression of the intestinal TLR5,NLRP3,caspase1 and NF-κB,thereby reduce the production of inflammatory factors,and reduce the inflammatory response. |
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