This study was conducted to evaluate the supplemental effects of esterified monobutyrin (MB) and tributyrin (TB) on growth performance, feed efficiency, digestibility, innate immunity, antioxidant status and disease resistance of Pacific white shrimp, Litopenaeus vannamei. A basal (control) experimental diet was formulated without MB or TB, and four other diets were prepared by supplementing powder forms of MB at 2 and 4 g/kg (0.2% and 0.4%) or TB at 1 and 2 g/kg (0.1% and 0.2%) (designated as MB0.2, MB0.4, TB0.1 and TB0.2, respectively). Quadruplicate groups of shrimps were hand‐fed with one of the diets four times daily for 53 days. Shrimp fed MB or TB diets showed significantly higher growth performance, feed utilization, phagocytosis and glutathione peroxidase activity than shrimp fed the control diet. Increased digestibility of dietary protein, lipid and dry matter was found in shrimp fed MB‐ or TB‐supplemented diets. Relative mRNA expression levels of IGF‐binding protein and prophenoloxidase gene were significantly increased in shrimp fed MB‐ or TB‐supplemented diets than in shrimp fed the control diet. The results of a challenge test with Vibrio harveyi showed that the disease resistance of shrimp can be significantly enhanced against V. harveyi when they were fed TB0.2 diet. The results of this study indicate that dietary supplementation of 2 g/kg MB or 1–2 g/kg TB can improve growth and feed efficiency, innate immunity, antioxidant activity, digestibility and disease resistance of L. vannamei.
The supplemental effect of marine algae (Ulva spp. and Solieria spp.) extracts with/without organic acids was evaluated in olive flounder (Paralichthys olivaceus) diet. A diet containing 55% fish meal was considered as the control diet. Three other diets were prepared by supplementing 0.5% of algae extract from Ulva spp. mixed with a blend of organic acids and 0.3% or 0.5% algae extracts from Ulva spp. and Solieria spp. into the control diet (CON, AS5, AL3 and AL5). Total 640 fish (initial mean body weight: 26.5 ± 0.02 g) were randomly distributed into 16 tanks as 40 fish per tank. Quadruplicate groups of fish were hand‐fed one of the experimental diets twice a day for 12 weeks. Growth performance of fish was not significantly affected by experimental diets although feed utilization of fish fed AS5 diet was significantly higher than that of the CON group. The innate immune responses and activities of antioxidant enzymes were significantly increased by dietary supplementation of the additives. When fish were challenged with Edwardsiella tarda, survival was higher in fish fed the additive supplemented diets than the CON group. Catalase, lysozyme and superoxide dismutase activities were significantly higher in surviving fish fed the additive supplemented diets than the CON group after the challenge test. Goblet cell counts in fish intestine were significantly higher in AS5 group. Amylase and lipase activities and lipid digestibility were increased by the diets containing additives. The findings in this study indicate that algal extract and/or organic acid supplementation in diets increase innate immunity, disease resistance, intestinal morphology, digestive enzyme activity, diet digestibility and feed utilization of olive flounder.
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