| As an ecologically and environmentally friendly microecological preparation,probiotics have a very broad application prospect in improving the immunity of aquatic animals and replacing antibiotics.Probiotics are usually defined as living or inactivated,single or compound microorganisms,which can improve the health of aquatic animals.However,there are few studies on the effects of heat-killed Lactobacillus plantarum and compound probiotics on the antioxidant capacity,intestinal morphology and intestinal microbiota of Litopenaeus vannamei.Therefore,this study aims to explore the effects of a heat-killed L.plantarum and different forms of compound probiotics on the growth,non-specific immunity,antioxidant capacity,disease resistance,intestinal morphology and intestinal microbiota health of L.vannamei,so as to explore its application potential in shrimp aquaculture,and provide theoretical reference for large-scale healthy green culture of shrimp in actual production.The main results of this study were as follows:Experiment 1: Effects of dietary heat-killed L.plantarum and compound probiotics on the growth performance,antioxidant enzymes,and intestinal health of L.vannameiThis study was conducted to evaluate the effects of dietary heat-killed L.plantarum and compound probiotics(GH35A and GH35B)on the growth,antioxidative capacity,intestinal morphology,and microbiota of L.vannamei.Shrimps(1.29 ±0.01 g)were fed with five different diets: C(control,basal diet without probiotics),LP1(basal diet supplemented with 0.05%heat-killed L.plantarum powder),LP2(basal diet supplemented with 0.1% heat-killed L.plantarum powder),T1(basal diet supplemented with 15% GH35 A and 1% GH35B),and T2(basal diet supplemented with 15% GH35 A and 2% GH35B).After 28 days of the feeding trial,compared with group C,the final body weight and body weight gain of group LP2 were the highest(P > 0.05).It was also observed that the final body weight,body weight gain,specific growth rate,condition factor,and intestinal-somatic index were significantly higher in T1 and T2 compared to those observed in group C(P < 0.05).The feed conversion ratio in LP1 and LP2 groups was lower than that of group C(P > 0.05),while that in T1 and T2 groups was significantly lower than that in group C(P < 0.05).The condition factor and intestinal-somatic index in LP1 and LP2 were significantly higher than those in C(P < 0.05).In addition,the hepato-somatic index of all groups except T2 was significantly higher than that in C(P < 0.05).The total antioxidant capacity in LP1 and T1 was significantly higher than that in C(P < 0.05).It was found that the activity of total superoxide dismutase in groups C,LP1 and LP2 was the highest in group LP2(P > 0.05),and it was significantly lower in group C than in T1 and T2groups(P < 0.05).The peroxidase activity of T1 was significantly higher than that in C and T2(P < 0.05).Besides,the total nitric oxide synthase activity in LP2 group was higher than that in LP1 group(P < 0.05).The activity of polyphenol oxidase in C was significantly lower than that in LP1,LP2 and T2(P < 0.05).The activities of acid phosphatase and alkaline phosphatase in LP2,T1 and T2 were significantly higher than those in C(P < 0.05).The lipase activity of group T2 was the highest,and higher than that in group C(P < 0.05).The intestinal villus height in all experimental groups was higher than that in group C(P < 0.05),the intestinal villus width and intestinal wall thickness of LP1 and T2 were significantly higher than those in C(P < 0.05).Overall,the intestinal villus structure of LP2 and T2 groups was well developed,while the group C was disordered and smooth.The dominant phyla in L.vannamei were Proteobacteria and Bacteroidetes,the abundances of Verrucomicrobia and Firmicutes were the lowest in C group,and showed a higher level of Phanerochaete.Haloferula,which was the most abundant in LP2 and T1.Chao 1 and Ace indexes were the highest in LP2 group,Shannon index in LP1 group was higher than that in LP2 and C group,and Simpson index in C group was the highest.Chao 1,Ace indexes and Simpson index in T2 group were higher than those in group C,and Shannon index was the highest in group C.Experiment 2: Effects of different forms of compound probiotics on the growth performance,antioxidation capacity,disease resistance,and intestinal health of L.vannameiThis study was conducted to evaluate the effects of different forms of compound probiotics(non-inactivated and inactivated)on the growth performance,antioxidative capacity,disease resistance,intestinal morphology,and microbiota of L.vannamei.Shrimps(0.40 ± 0.00 g)were fed with five different diets: C(control,basal diet without probiotics),T1(basal diet supplemented with 0.5% non-inactivated compound probiotics),T2(basal diet supplemented with 2% non-inactivated compound probiotics),H1(basal diet supplemented with 0.5%heat-killed compound probiotics),and H2(basal diet supplemented with 2% heat-killed compound probiotics).After 35 days of the feeding trial,the final body weight,body weight gain and specific growth rate in T2 group were the highest,followed by T1,which were significantly higher than those in C(P < 0.05).The above indexes in H1 and H2 were significantly higher than those in C(P < 0.05),and those in H1 were significantly higher than those in H2(P < 0.05).The feed conversion ratio in group C was significantly higher than that in other experimental groups(P < 0.05),and the minimum values appeared in T2 and H1 groups,respectively.The condition factor in T1,T2 and H1,H2 groups was significantly higher than that in group C(P <0.05).Except for H1,the hepato-somatic index of all experimental groups was significantly higher than that in C(P < 0.05).The total antioxidant capacity and total superoxide dismutase activity in C were significantly higher than those in other groups(P < 0.05),and the minimum values appeared in T1 and H1 groups,T1 and H2 groups,respectively.The peroxidase activity of each experimental group was significantly higher than that in C(P < 0.05),and the peaks appeared in groups T2 and H1(P < 0.05).In addition,the polyphenol oxidase activity in group C was significantly lower than that of the experimental groups(P < 0.05),and that of group H2 was significantly higher than that of group H1(P < 0.05).The acid phosphatase and alkaline phosphatase activities in T1,T2 and H2 were significantly higher than those in C(P < 0.05),and the acid phosphatase activity in group H1 was higher than that in group C(P < 0.05).The activities of lipase and amylase in group C were significantly lower than those in each experimental group(P < 0.05).The cumulative mortality rate in T1,T2 and H1 was significantly lower than that in C(P < 0.05).The relative percent survival of the experimental groups fed with non-inactivated compound probiotics and heat-killed compound probiotics was significantly higher than that in C(P < 0.05).The intestinal villus height and intestinal wall thickness in each experimental group were significantly higher than those in C(P < 0.05).Moreover,the intestinal villus width in C was significantly higher than that in T1 and T2(P < 0.05),while that in group T1 was higher than that in group T2(P < 0.05).However,the intestinal villus width in group H2 was significantly higher than that in C and H1 groups(P < 0.05),and that in group C was higher than that in H1 group(P < 0.05).The width of midgut villi in H2 group was significantly higher than that in C and H1 groups(P < 0.05),while that in C group was higher than that in H1 group(P < 0.05).On the whole,the intestinal villi in T2 and H2 groups were well developed,while the intestinal tissue structure in group C was disordered.Proteobacteria and Firmicutes were the dominant phyla in the intestine of L.vannamei,and the abundances of Actinobacteria and Verrucomicrobia in group C were the lowest.Except group T2,group C showed the highest level of Phanerochaete,and the abundance of Bacteroidetes was the highest in group T1.Ruegeria was the most abundant in T2 and H2 groups,Haloferula in group C was lower than that in other groups,and Celeribacter in T2 and H1 groups was the highest.Chao 1 and Ace indexes were the highest in group C,followed by T2 and T1 groups;Shannon index in group T2 was higher than that in C and T1 groups;and Simpson index in group C was the highest.Also,Chao 1 and Ace indexes in H2 group were higher than those in H1 group,and Shannon and Simpson indexes were the highest in group C. |
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