Effects Of Two Lactic Acid Bacteria On The Growth And Immune Performance Of Micropterus Salmoides

Largemouth bass is favored for its non-muscular spines and delicious meat,and is widely farmed throughout the country,with an annual aquaculture output of more than 500,000 tons.In order to provide the public with healthy and environmentally friendly aquatic products,gre en,antibiotic-free and anti-resistant breeding has become the general trend,and lactic acid bac teria have significant probiotic functions and are ideal antibiotic substitutes.Lactobacillus pla ntarum and Pediococcus pentosaceus are two types of lactic acid bacteria,which have the cha racteristics of enhancing the immunity of animals and improving the intestinal function of ani mals.In this study,the effects of Lactobacillus plantarum LP-37 and Pediococcus pentosaceu s PP-23 were added to the basic feed of largemouth bass to compare the differential effects of two lactic acid bacteria on the growth and immune performance of largemouth bass,and provi de a basis for their application.In this experiment,600 largemouth bass with a size of 7.14±0.11g were divided into four test groups:C0,T1,T2 and T3.The C0 group was fed basal feed,the T1 group was fed1×10~8CFU/g Lactobacillus plantarum LP-37,the T2 group was fed 1×10~7CFU/g Pediococcus pentosaceus PP-23,and the T3 group was fed 1×10~8CFU/g Lactobacillus plantarum LP-37+1×10~7CFU/g Pediococcus pentosaceus PP-23,with three replicates of 50fish in each group.The growth results showed that the final body weight,weight gain rate and specific growth rate of T1,T2 and T3 groups were significantly higher than those in C0 group,the bait coefficient was significantly lower than that of C0 group,the difference between T1and T2 groups was not significant,the bait coefficient of T3 group was significantly lower than that of T1 and T2 groups,and the rest of the growth indexes were significantly higher than that of T1 and T2 groups.The body index results showed that the fatness and liver body index of T1,T2,and T3 groups were significantly higher than those of C0 group,and the visceral body fat number of T3 group was significantly higher than those of C0,T1,and T2groups,while there was no significant difference in intestinal body index among the four groups.The results of intestinal section showed that the villi height in the T1 and T3 groups was significantly higher than that in the C0 group,while the difference between the T2 group and the C0 group was not significant,the villi width in the T3 group was significantly higher than that in the C0,T1 and T2 groups,the thickness of the muscular layer in the T1,T2 and T3 groups was significantly higher than that in the C0 group,the difference between the T1and T2 groups was not significant,and the T3 group was significantly higher than that in the T2 group.The enzyme activity test results showed that the serum enzymes AKP,ACP,SOD,PRS,LPS,and AMS in T1,T2,and T3 groups were significantly higher than those in C0group,while the enzyme activity in T3 group was significantly higher than that in T1 and T2groups.In terms of liver antioxidant,the activities of CAT and SOD in groups T1,T2 and T3were higher than those in group C0,and the content of MDA was significantly lower than that in group C0,the activities of CAT and SOD in group T3 were significantly higher than those in groups T1 and T2,and the content of MDA was significantly lower than that in groups T1and T2.The results of growth-related gene assays showed that the GH gene expression in T1and T3 groups was significantly higher than that in C0 group,while the difference between T2 group and C0 group was not significant,and the expression of IGF-1 gene in T1,T2 and T3 groups was significantly higher than that in C0 group,but the difference between the three groups was not significant.The results of immune-related gene assays showed that in the head kidney,the expression of pro-inflammatory factors such as IFN-γ,TNF-α,IL-8 and IL-1βin the T1,T2 and T3 groups was significantly lower than that in the C0 group,but the difference between the three groups was not significant,the expression of anti-inflammatory factors such as IL-10 and TGF-1βwas significantly higher than that in the C0 group,the difference between T1 and T2 groups was not significant,and the expression of TGF-1βfactors in T3group was significantly higher than that in T1 and T2 groups.In the spleen,the expression of pro-inflammatory factors such as IFN-γ,TNF-α,IL-8 and IL-1βin the T1,T2 and T3 groups was significantly lower than that in the C0 group,the expression of anti-inflammatory factors such as IL-10 and TGF-1βwas significantly higher than that in the C0 group,the difference between the T1 and T2 groups was not significant,the expression of pro-inflammatory factors in the T3 group was significantly lower than that in the T1 and T2 groups,and the expression of anti-inflammatory factors was significantly higher than that in the T1 and T2 groups.The above results indicate that the addition of Lactobacillus plantarum LP-37 and Pediococcus pentosaceus PP-23 to the feed could significantly improve the growth performance,serum activity,digestive enzyme activity and liver antioxidant function of largemouth bass,and also significantly upregulate the expression of GH,IGF-1 gene and anti-inflammatory factors IL-10 and TGF-1βin largemouth bass,downregulate the expression of pro-inflammatory factors IL-8,IL-1β,IFN-γand TNF-α,and increase the length,width and thickness of intestinal villi.Moreover,the combination of LP-37+PP-23 has a positive synergistic effect,which is significantly superior to the use of a single strain for the probiotic effect of largemouth bass.