低盐胁迫下饲料中添加 α-硫辛酸对凡纳滨对虾生长、抗氧化能力及肠道健康的影响

This experiment was conducted to study the effects of dietary α⁃lipoic acid (α⁃LA) on growth, an⁃ tioxidant capacity and intestinal health of Litopenaeus vannamei under Low Salinity Stress. A total of 1 000 ju⁃ venile Litopenaeus vannamei with initial body weight of (0. 061 ± 0. 005) g were randomly divided into 5 groups with 4 replicates in each group and 50 juvenile shrimp in each replicate. Two control groups (25%o sea⁃ water control group and 3%o low salinity control group) were fed the basal feed, and the experimental groups were fed experimental diets which containing 0.3, 0.6 and 1.2 g / kg α⁃LA at 3%o salinity, respectively. The experiment lasted for 8 weeks. The results showed as follows: 1) the survival rate of 3%o low salinity control group was significantly lower than that of 25%o seawater control group (P<0.01), and significantly lower than that of 1.2 g / kg α⁃LA group (P<0.05) . The hepatosomatic index of 3%o low salinity control group and 0.3, 0.6, 1.2 g / kg α⁃LA groups was significantly lower than that of 25%o seawater control group (P<0.05) . The condition factor of 1.2 g / kg α⁃LA group was significantly lower than that of 3%o low salinity control group and 25%o seawater control group (P<0.05) . 2) Compared with 3%o low salinity control group, the content of ma⁃ londialdehyde (MDA) in hepatopancreas of 1.2 g / kg α⁃LA group was significantly decreased (P<0.05), the activity of superoxide dismutase (SOD) in hepatopancreas of 0.6 and 1.2 g / kg α⁃LA groups was significantly increased (P<0.05), and the activity of lactate dehydrogenase (LDH) in hepatopancreas of 1.2 g / kg α⁃LA group was significantly decreased (P<0.05) . 3) The intestinal flora Simpson and Shannon indexes of 1.2 g / kg α⁃LA group were significantly lower than that of 25%oseawater control group (P < 0. 05), but significantly higher than that of 3%o low salinity control group (P<0.05); the intestinal flora Chao1 and ACE indexes of 1.2 g/ kg α⁃LA group was significantly higher than that of 25%o seawater control group and 3%o low salinity control group (P<0.05 or P<0.01). 4) Compared with 25%o seawater control group, the relative abundance of Bacteroides in intestine of 3%o low salinity control group was significantly increased (P<0.05), while the relative abundances of Proteobacteria and Fusobacteria in intestine were significantly decreased (P<0.05); the relative abundances of Flavobacterium, Actibacter, Tropicimonas and Shinella in intestine of 1.2 g/ kg α⁃ LA group were significantly increased (P<0.05). Compared with 3%o low salinity control group, the relative abundances of Firmicutes and Actinobacteria in intestine of 1.2 g/ kg α⁃LA group were significantly increased (P<0.05), and the relative abundances of Flavobacterium, Shinella and Actibacter in intestine were signifi⁃ cantly increased (P<0.05). 5) The results of heat map cluster analysis of intestinal microbial abundance at ge⁃ nus level showed that compared with 3%o low salinity control group, the relative abundances of Tenacibacu⁃ lum, Rhodobacter and Rheinheimera in intestine of 1.2 g/ kg α⁃LA group were significantly decreased (P< 0.05), while the relative abundances of Donghicola, Haloferula, Marivita and other genus in intestine were significantly increased (P<0.05). Most of the significant differential genes of intestinal microorganisms predic⁃ ted by PICRUSt were related to metabolic pathways, compared with 3%o low salinity control group, the genes encoded by intestinal microorganisms of 1. 2 g/ kg α⁃LA group were significantly enriched in the metabolic pathways related to vasopressin⁃regulated water reabsorption, Fc gamma R⁃mediated phagocytosis and endocy⁃ tosis. Thus it can be seen that α⁃LA can be used as a feed additive to help Litopenaeus vannamei cope with low salinity stress.