Effects Of Lactobacillus Plantarum LP-37 Combined With Florfenicol On Growth And Immunity Of Sebastes Schlegelii

Lactobacillus plantarum is a common probiotic in aquaculture,and florfenicol is a common antibiotic in aquaculture,which have great influence on fish growth and immunity.This experiment was conducted to study the effects of feeding Lactobacillus plantarum and florfenicol on the intestinal microflora diversity,immune gene expression,serum digestive enzyme activity,serum immune enzyme activity,intestinal microflora abundance,and serum metabolites of Sebastes schlegelii.The experiment used Lactobacillus plantarum LP-37 labeled with GFP green fluorescent protein,and selected 400 Sebastes schlegelii with an average weight of(32.23±9.38)g from the same batch.They were randomly divided into 4 groups,recorded as control Group 0,test Group 1,Group 2,and Group 3,for a 30 day aquaculture experiment.The experimental group0 was fed with basic feed,the experimental Group 1 was mixed with 10~7 CFU/ml of Lactobacillus plantarum in the feed,and the experimental Group 2 was mixed with 20 mg/kg of florfenicol.Test Group 3 was fed with 20 mg/kg of florfenicol from day 1-15 and 10~7 CFU/ml of Lactobacillus plantarum from day 16-30.The growth indicators,digestive enzyme activity,immune enzyme activity,and immune related gene expression changes of Sebastes schlegelii and its intestinal contents,kidneys,liver,and blood samples in each group were measured for analysis;Using 16S r DNA sequencing and metabolomics techniques,the changes in intestinal microflora and metabolites of Sebastes schlegelii in each group were determined,and the results were as follows:(1)Effects of adding Lactobacillus plantarum and florfenicol to feed on growth performance of Sebastes schlegelii:Compared with Group 0,the terminal weight and average weight gain of each experimental group increased significantly,with the average weight gain of Group 1 increased by 39.24%,Group 2 increased by 54.41%and Group 3 increased by47.28%.(2)Effects of adding Lactobacillus plantarum and florfenicol to feed on digestive enzyme activities of Sebastes schlegelii:compared with the test Group 0α-The activity of AMS was significantly increased(P<0.05);The LPS activity of each test group decreased significantly(P<0.05);The Trypsin activity in Group 1 and Group 3 test groups was significantly lower than that in Group 0 test group,and trypsin activity in Group 2 test groups was significantly higher than that in test group(P<0.05).(3)Effect of adding Lactobacillus plantarum and florfenicol to feed on immune enzyme activities of Sebastes schlegelii:compared with the test Group 0,the AKP activity of Group 1,Group 2 test groups increased significantly;The activity of SOD enzyme in each test group was significantly increased(P<0.05).(4)Effects of Lactobacillus plantarum and florfenicol on the expression of immune-related genes of Sebastes schlegelii:compared with the blank control Group 0,The expression of immune genes IRAK-4 and MYD88 in liver of Group 2 were significantly up-regulated(P<0.05),while those in Group 1 and Group 3 were significantly down-regulated(P<0.05).In kidney,the expressions of immune genes IRAK-4 and MYD88 in Group 2 were significantly up-regulated(P<0.05),while those in Group 1 and Group 3 were significantly down-regulated(P<0.05).(5)Effects of adding Lactobacillus plantarum and florfenicol to the diet on the intestinal microbial structure of Sebastes schlegelii:16S r DNA sequencing analysis showed that the species abundance at the level of the Group 1,Group 2,and Group 3 groups increased compared to the control Group 0.Compared with Group 0,the number of intestinal microflora taxon(OTU)in Group 1 group increased slightly,and the number of OTU in Group 2 and Group 3was significantly higher than that in control Group 0;In Group 1,the relative abundance of Firmicutes increased,while Proteobacteria,Bacteroides,and Cyanobacteria decreased;In Group 2,the relative abundance of Firmicutes and Acidobacillus increased,while the relative abundance of Verrucomycetes and Proteobacteria decreased;In Group 3,the relative abundance of Proteobacteria and Acidobacillus increased,while the relative abundance of Verrucomycetes decreased.(6)Effects of adding Lactobacillus plantarum and florfenicol to the diet on the metabolism of Sebastes schlegelii:Compared with Group 0,the relative contents of glycolipid,fatty acid,tryptamine and choline metabolites decreased,while the relative contents of heterocyclic compounds increased in Group 1.The relative content of glycolipid in Group 2 decreased;The relative contents of glycolipids,fatty acids,tryptamine metabolites and choline metabolites decreased in Group 3.In summary,adding 10~7 CFU/ml of Lactobacillus plantarum LP-37 and 20 mg/kg of florfenicol can improve the growth performance,immune enzyme activityα-AMS activity,intestinal microflora abundance,and reducing the relative content of glycolipids in plasma metabolites.Adding Lactobacillus plantarum LP-37 decreased LPS activity,increased trypsin activity,decreased expression levels of immune genes IRAK-4 and MYD88,increased intestinal microflora abundance,and decreased relative content of glycolipids and fatty acids in plasma metabolites;Adding florfenicol decreased LPS activity,increased trypsin activity,increased expression levels of immune genes IRAK-4 and MYD88,increased intestinal microflora abundance,and decreased the relative content of glycolipids in plasma metabolites;The effect of adding Lactobacillus plantarum and florfenicol in combination is different from that of adding Lactobacillus plantarum and florfenicol alone.This experiment has once again verified the prebiotic effect of Lactobacillus plantarum on fish and animals,demonstrating the growth and immune promoting effects of low concentration florfenicol on Sebastes schlegelii in a short period of time.