Effects Of Compound Probiotics On Intestinal Microbial Composition And Intestinal Injury Induced By Stress In Broilers

The intestine is an important organ for animal nutrition digestion and absorption,and is also one of the main sites of immune response.It is an important factor for intestinal health in ensuring the health and production performance of livestock.Probiotics are a class of active microorganisms that colonize the intestine and exert a beneficial effect on the host.Alfafa powder is cheap and rich in high-quality fiber,which is beneficial to intestinal microbial fermentation and thus improves intestinal health.However,the combined use of probiotics and alfalfa meal in broiler production is not clear.The intensive production model of livestock brings a variety of stressors.Among them,and bacterial infection and chronic stress seriously affect the welfare status and intestinal health of broilers,and ultimately lead to a decrease in production performance.Therefore,the aim of this study was to investigate the effects of early exposure to probiotics on the composition of gut microbes in the small intestine of broilers,and the protecting effects of probiotcs on the intestinal injury induced by two different kinds of stress in broilers.In this study,LPS(lipopolysaccharide)and Cort(corticosterone)were used to simulate pathogen infection stress and chronic stress to induce the intestinal damage,and to further explore the effect of early exposure to probiotics on protecting the intestinal health and the related mechanisms.1、Effect of Prob and Alfa on performance of broilersThe experiment selected 192 1-d-old green-footed chickens and divided into 4 groups,namely,control group(Con),probiotic group(Prob),alfalfa group(Alfa),probiotics and alfalfa co-treatment group(Prob&Alfa),6 replicates per group,8 chickens per replicate.At 2 days of age,the Prob treatment group was added with Probiotics at a dose of 60 mg/day/day for 2 weeks;at 22 days of age,Alfa group broilers were fed 4%Alfalfa in feed and fed for 3 weeks.At 44 days of age,blood,intestinal contents and mucosal epithelial tissues were collected.The results showed that compared with the control group,the addition of Prob and Alfa alone increased ADG of broilers(P<0.05),the Prob&Alfa group reduced FCR of broilers.Prob and Alfa treatment had no significant effect on broiler slaughter performance and immune performance(P>0.05).Prob and Alfa treatment increased the cecal microbial diversity of broiler chickens and increased the bacterial abundance ratio of Bacteroides and Firmicutes,and increased the abundance of Lactobacillus bacteria,but the difference was not significant(P>0.05).Among them,Alfa treatment significantly increased the abundance of Fusobacterium bacteria(P<0.05).Real-time quantitative PCR showed that early Prob treatment increased the mRNA expression of Occludin gene in duodenum of broilers;Alfa treatment significantly decreased the mRNA expression of SGLT1,GLUT2,GLUT5,B0AT and EAAT3 genes(P<0.05).The above results suggest that early Prob treatment and Alfa treatment can improve the diversity of cecal microbes and promote the colonization of Bacteroides;early Prob treatment and Alfa treatment can improve the feed utilization rate of broilers,but combined use to reduce broiler production performance.2、Effect of Prob on LPS-induced intestinal damage in broilersThe experiment selected sixty 1-d-old Rose 308 white feather broilers and divided into four groups:control group(Con),LPS group(LPS),probiotic group(Prob),probiotics and LPS co-treatment group(Prob&LPS).At 2 days of broiler,the Prob treatment group was added with Probiotics at a dose of 50 mg/day/day for 2 weeks;the LPS injection test was performed at the age of 29 days,and the injection dose was 0.5 mg/kg,which was intraperitoneally injected.Sampling started after 2 hours.The results showed that LPS treatment significantly reduced jejunum villus length and goblet cell density(P<0.05),and decreased the expression of Occludin and ZO1 mRNA in jejunum;early Prob treatment significantly increased jejunal villus length and crypt depth(P<0.05).LPS treatment significantly increased the expression of Caspase3 and BAX mRNA in jejunum,and increased the positive rate of apoptotic cells and Caspase3 activity(P<0.05).Early Prob treatment can significantly reduce the expression of Caspase3 mRNA and enzyme activity in intestinal mucosa caused by LPS.These results suggest that LPS treatment can cause intestinal mucosal barrier damage and induce intestinal epithelial cell apoptosis;early Prob colonization has a certain alleviation effect on LPS-induced intestinal epithelial cell apoptosis.3、Effect of Prob on Cort-induced intestinal injuryThe experiment selected 192 1-d-old green-footed chickens and divided into 4 groups,namely control group(Con),probiotic group(Prob),corticosterone group(Cort),probiotic and corticosterone co-treatment group(Prob&Cort),6 replicates per group,8 chickens per replicate.At 2 days of age,the Prob treatment group was added with Probiotics at a dose of 100 mg/day/day for 2 weeks;at 28 days of age,the chickens in the Cort-treated group were injected at a dose of 4 mg/kg/d,and the neck was injected subcutaneously for 7 days.At 35 days of age,broilers were slaughtered to collect blood and intestinal epithelial tissue.The results showed that Cort treatment significantly increased duodenal villus height,significantly decreased duodenal TJs mRNA expression,and significantly increased duodenal mucosal IL-10 mRNA expression(P<0.05).In addition,Cort had a tendency to decrease the anti-oxidation index of SOD in duodenal mucosa(0.05<P<0.1).Cort treatment significantly reduced jejunum villus length and significantly decreased trypsin activity and genes expression levels of TJs,EGFR,IL-1β NLRP3 in jejunum mucosa(P<0.05).Prob treatment significantly increased the expression of BCL-2 genes in duodenal mucosa of broilers,and significantly increased the length of jejunum villus and the genes expression of Occludin and PepT1 in jejunum mucosa.The above results suggest that Cort can cause intestinal mucosal barrier damage in broilers,and Prob has a certain alleviation effect on this negative effect,but there are inter-tissue differences in this effect.