关键词: 植物乳杆菌, 羔羊, 抗氧化能力, 肠道黏膜屏障, 肠道菌群

Abstract:

The aim of the experiment was to investigate the mitigatingregulating effect of Lactobacillus plantarum on diarrhea lambs in indexes including the damage of anti-oxidative capacity in serum, jejunal microbiota, and jejunal mucosal barrier damagein diarrhea lambs. Twenty-four newly weaned lambs were selected and distributed into four groups using a completely randomized experimental design: the control group (C), the diarrhea group (D), the group of antibiotic-treated under diarrhea (DA), and the group of Lactobacillus plantarum-treated under diarrhea (DL), with six replicates in each group. Lambs in groups D, DA and DL were dosed with 20 mL of ETEC K99 starting on the first day of the formal trial for 8 d consecutively. On the morning of the ninth day, lambs in group DA were injected regulated with florfenicol, and lambs in group DL were regulated by dosinggavaged with Lactobacillus plantarum, and the regulationabove treatment lasted for 4 consecutive days. The blood was collected fasting on days 1, 9 and 13 of the trial for the detection of serum antioxidant indexes as well as diamine oxidase (DAO) and D-lactic acid (D-LA) concentration in lambs. After slaughter the jejunal content was collected to determine the composition of bacterial community. The jejunal mucosal were collected to explore the expression of intestinal mucosal barrier-associated proteins and mucus proteins. Alisin Blue staining was uesd to study the changes of acidic mucus. The results showed that: 1) After 8 d of ETEC K99 treatment, the feces of lambs in D, DA and DL were all shapeless, and the concentrations of DAO and D-LA in the serum of lambs in the three groups were significantly higher than those in group C (P < 0.05), which indicated that the model of diarrhea had been successfully constructed; 2) On the 9^th day, compared with that of group C, the T-AOC and SOD in serum of lambs in D, DA and DL groups decreased significantly (P < 0.05), and the MDA content increased significantly (P < 0.05). Compared to on the 9^th day, the antioxidant capacity of lambs in DA and DL groups increased significantly on the 13^th day (P < 0.05), but there were significant decrease on the concentration of DAO, D-LA and MDA in serum of lambs in these two groups (P < 0.05);3) Compared to group C, the expression of Occludin, Claudin1 and MUC2 protein in group D decreased significantly (P < 0.05). Compared with group D, the expression of Occludin protein in jejunal tissues of DA lambs was significantly higher (P < 0.05), but the expression of Claudin1 and MUC2 proteins reduced slightly (P>0.05). The expression of Occludin, Claudin1 and MUC2 protein in DL group were significantly higher than that of DA group (P < 0.05). 4) Compared with group C, the Chao and Shannon values of the bacterial community in the jejunal content of lambs in D and DA decreased significantly (P < 0.05), and while increased in DL group (P>0.05).The abundances of Firmicutes in the jejunum of lambs from C, D and DL groups were significantly higher than in DA group (P>0.05). The abundances of Actinobacteriota in the jejunum of lambs was significantly higher in C, D and DA than in DL group (P < 0.05). The abundances of Proteobacteria in the jejunum of lambs was a little higher in D group than in C and DL groups (P>0.05), while the abundances of Proteobacteria in the jejunum of lambs in group DA was significantly higher than in C, D and DL groups(P < 0.05). Correlation analysis revealed that more microorganisms associated with MUC2 expression and the phylum Proteobacteria abundance was significantly negatively correlated with the expression of MUC2 protein (P < 0.05), while the phylaabundance of Firmicutes and Verrucomicrobiota were significantly positively correlated with the expression of MUC2 protein (P < 0.05). NK4A214_group had a significant positive correlation with MUC2 expression (P < 0.05) and Escherichia-Shigella was significantly negatively correlated with MUC2 expression (P < 0.05). In conclusion, ETEC K99 induced diarrhea in lambs, decreased serum antioxidant capacity and microbial diversity of jejunal content, and inhibited the expression of jejunal mucus barrier protein. Compared to antibiotic therapy, gavaging Lactobacillus plantarum increases the diversity of jejunal contents flora and promotes the expression of jejunal acidic mucus and mucus tissue barrier proteins. Above all, Lactobacillus plantarum had a better effect in improving lamb diarrhea.

Key words: Lactobacillus plantarum, lambs, anti-oxidative capacity, mucosal barrier of jejunum, bacterial community