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Vitamin E (tocopherols, VE) is a lipid-soluble antioxidant involved in neutralizing reactive oxygen species and maintaining immune function in animals. This study aimed to determine the optimum dietary VE requirement of juvenile Pacific white shrimp ( Penaeus vannamei ) for growth, feed utilization, immune responses, antioxidative capacity, diet digestibility, intestinal histomorphology and disease resistance against Vibrio parahaemolyticus . Eight experimental diets were formulated to contain graded levels of VE (0, 20, 40, 60, 80, 100, 120 and 240 mg/kg; designated as VE0, VE20, VE40, VE60, VE80, VE100, VE120 and VE240). Four replicate groups, each containing 30 shrimp (0.20 ± 0.04 g), were fed one of the diets six times daily for 56 days. Shrimp fed VE80 diet exhibited significantly increased growth performance compared to shrimp fed VE0, VE20 and VE240 diets. Non-specific immune responses were significantly enhanced in shrimp fed VE60-VE80 diets. Hepatopancreatic lipid peroxidation in VE80 group was significantly lower compared to the VE0 group. The expression of Crustin , C-MnSOD and GPx genes in the hepatopancreas was significantly upregulated in VE80 group. Graded dietary VE levels significantly linearly increased hemolymph and hepatopancreas VE concentrations. Intestinal villi height and width were significantly improved with dietary VE supplementation. The digestibility of protein, lipid and dry matter was significantly higher in shrimp fed VE80 diet compared to those fed VE0 diet. The resistance against V. parahaemolyticus was significantly higher in shrimp fed VE80, VE100 and VE120 diets compared to those fed VE0 and VE20 diets. The optimal dietary VE level for Pacific white shrimp was estimated to be 72.17 mg/kg for weight gain and 72.21 mg/kg specific growth rate, based on broken-line analysis. In conclusion, optimal dietary VE supplementation enhances shrimp growth, immunity, antioxidative defense and disease resistance against V. parahaemolyticus , thereby reducing the risk of early mortality syndrome caused by acute hepatopancreatic necrosis disease.

A twelve-week feeding trial was conducted to investigate the effect of dietary supplementation of a functional immunostimulant mixture (FIM; nucleotides, β-glucan and vitamins C and E) on growth, feed utilization, innate immunity, digestive enzyme activity, hematological parameters, intestinal morphology and inflammatory gene expressions of olive flounder, Paralichthys olivaceus. A fish meal-based basal diet (control) was formulated, and three other diets were prepared by incorporating 0.5, 1.0 and 1.5% FIM into the basal diet (HB0.5, HB1.0 and HB1.5, respectively). Five replicate groups of fish (26.3 ± 0.1 g) were fed one of the experimental diets. Inclusion of 1.5% FIM in the diet significantly enhanced growth and feed utilization. Significantly higher plasma hemoglobin, hematocrit, total protein levels and lower plasma glucose level were observed in the HB1.5 group. Total immunoglobulin content, lysozyme, nitroblue tetrazolium, myeloperoxidase, superoxide dismutase, glutathione peroxidase and catalase activities and immune-related gene expressions of toll-like receptor and perforin were significantly increased at the highest inclusion level. FIM supplementation significantly increased villus height and goblet cell counts. Anti-inflammatory gene expressions were significantly upregulated at a 1.5% level. Dietary supplementation of 1.5% of FIM could improve growth and feed utilization, immune, hematological and intestinal histomorphological parameters of olive flounder.

This study assessed the effects of dietary supplementation of poly-β-hydroxybutyrate (PHB) on growth performance, feed efficiency, non-specific immunity, digestive enzyme capacity, phagocytic activity, hemocyte count, intestinal morphology, and disease resistance against Vibrio parahaemolyticus of Pacific white shrimp (Penaeus vannamei). Six diets were prepared by supplementing graded levels of PHB at 0.00, 0.25, 0.50, 1.00, 2.00, and 4.00% (Con, P0.25, P0.5, P1.0, P2.0, and P4.0, respectively). Triplicate groups of 90 shrimps (initial body weight 0.25 ± 0.01 g) per treatment were randomly assigned and fed an experimental diet for 56 days. The growth performance of shrimp was significantly improved by 1% dietary PHB supplementation. PHB-included diets fed shrimp showed significantly improved hepatopancreatic trypsin, chymotrypsin, and pepsin activities. Villus height was significantly increased with dietary PHB supplementation, and villus width was increased at a 1% inclusion level. P0.25, P0.5, and P4.0 groups significantly increased phenoloxidase activity, and the P2.0 group significantly increased anti-protease activity compared to the Con group. The survival of shrimp challenged against V. parahaemolyticus was higher in P0.5, P1.0, and P2.0 groups than in the Con diet. Dietary PHB supplementation improved weight gain, digestive enzyme activity, intestinal morphology, non-specific immunity, and disease resistance against V. parahaemolyticus of shrimp. According to the above observations, the optimal dietary PHB supplementation level for maximum weight gain would be 1% for Pacific white shrimp.

A twelve-week feeding trial was conducted to investigate the effect of dietary supplementation of a functional immunostimulant mixture (FIM; nucleotides, β-glucan and vitamins C and E) on growth, feed utilization, innate immunity, digestive enzyme activity, hematological parameters, intestinal morphology and inflammatory gene expressions of olive flounder, Paralichthys olivaceus. A fish meal-based basal diet (control) was formulated, and three other diets were prepared by incorporating 0.5, 1.0 and 1.5% FIM into the basal diet (HB0.5, HB1.0 and HB1.5, respectively). Five replicate groups of fish (26.3 ± 0.1 g) were fed one of the experimental diets. Inclusion of 1.5% FIM in the diet significantly enhanced growth and feed utilization. Significantly higher plasma hemoglobin, hematocrit, total protein levels and lower plasma glucose level were observed in the HB1.5 group. Total immunoglobulin content, lysozyme, nitroblue tetrazolium, myeloperoxidase, superoxide dismutase, glutathione peroxidase and catalase activities and immune-related gene expressions of toll-like receptor and perforin were significantly increased at the highest inclusion level. FIM supplementation significantly increased villus height and goblet cell counts. Anti-inflammatory gene expressions were significantly upregulated at a 1.5% level. Dietary supplementation of 1.5% of FIM could improve growth and feed utilization, immune, hematological and intestinal histomorphological parameters of olive flounder.

The supplementary effects of an emulsifier mixture (polyoxyethylene (20) sorbitan monolaurate and distilled monoglycerides) were investigated on feed utilization, growth performance, and immunity of olive flounder, Paralichthys olivaceus, replacing fish oil with beef tallow. A fish oil containing diet was considered as positive control (PC) and a diet containing beef tallow instead of fish oil was considered as negative control (TW). Two other diets (EM01 and EM02) were prepared by adding 0.01 and 0.02% of the emulsifier into the TW diet. After 8 weeks of a feeding trial, growth performance and feed utilization were significantly higher in fish fed EM01, EM02, or PC diets compared to those fed the TW diet. Dry matter digestibility was higher in EM01 and EM02 diets than the TW diet and comparable to PC diet. Lipid digestibility was significantly higher in PC diet compared to TW diet. Liver EPA and DHA levels were lower, and oleic acid level was higher in fish fed diets containing tallow compared to PC group. Significantly increased aspartate aminotransferase and triglyceride levels were observed in TW group. Dietary supplemented emulsifier restored the reduced performance of olive flounder fed diets containing tallow instead of fish oil. However, the optimum inclusion level of the emulsifier should be elucidated in future studies.