Reevaluation of the Dietary Protein Requirement of Japanese Flounder Paralichthys olivaceus

An experiment was conducted to determine the dietary protein requirement by different analysis methods and to study the effects of dietary protein levels on growth performance and body composition in Japanese flounder Paralichthys olivaceus fed white fish meal and casein-based diets for 8 wk. After a 1-wk conditioning period, one of six isocaloric diets containing 30, 36, 42, 48, 54, and 60% crude protein (CP) was fed to fish at approximately 4–5% of wet body weight on a dry matter basis to triplicate groups of 15 fish averaging 13.3 ± 0.06 g (mean ± SD). After 8 wk of the feeding trial, weight gain (WG) and feed efficiency (FE) from fish fed 48% CP diet were similar to those from fish fed 42% and 54% CP diets, and were significantly higher than those from fish fed 30, 36 and 60% CP diets ( P < 0.05). Fish fed 48 and 54% CP diets had a significant higher specific growth rate (SGR) than did fish fed 30 and 36% CP diets ( P 0.05). Protein efficiency ratio (PER) was inversely related to the dietary protein level. No significant differences existed in hematocrit (PCV) and survival rate among the dietary treatments. Broken-line model analysis indicated that the optimum dietary protein level could be 44.0 ± 3.0% for maximum WG in Japanese flounder. Polynomial regression analysis of the dose-response showed that maximum WG occurred at 50.2% ( R² = 0.94) based on WG, and the second-order polynomial regression analysis with 95% confidence limits revealed that the range of minimum protein requirement was between 38.9% and 40.3% based on WG. Therefore, these findings suggest that the optimum dietary protein requirement for maximum growth of Japanese flounder is greater than 40%, but less than 44% CP in the fish meal and casein-based diets containing 17.0 kJ/g of energy.     

Optimum dietary phosphorus level of juvenile Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> reared in the recirculating system

ABSTRACT:   An 8-week feeding trial was conducted to determine the optimum dietary phosphorus level of juvenile Japanese flounder Paralichthys olivaceus reared in the recirculating system. The basal diet containing 0.33% total phosphorus (TP) was supplemented with NaH₂PO₄·H₂O to provide 0.33, 0.51, 0.71, 0.94, 1.10 and 2.12% TP for the experimental diets. Fish averaging 2.0 ± 0.04 g (mean ± SD) were fed in triplicate groups with the experimental diets for 8 weeks. After 8 weeks, fish fed the 0.51% TP diet showed significantly higher weight gain (WG), feed efficiency (FE), specific growth rate (SGR), and protein efficiency ratio (PER) than those fed the 0.33% and 2.12% TP diets ( P  < 0.05). Meanwhile, no difference was observed in WG, FE, SGR and PER of fish fed the 0.51, 0.71, 0.94 and 1.10% TP diets. Fish fed the 0.33% TP diet showed phosphorus deficiency symptoms such as poor growth and a deformed head by the end of 8 weeks. Ash and phosphorus contents of bone increased with the increase of dietary phosphorus concentrations. anova test, the quadratic regression analysis, and the broken line analysis suggested that the optimum dietary phosphorus level could be between 0.45 and 0.51% TP for maximum WG in juvenile Japanese flounder.     

Effects of different dietary levels of L-ascorbyl-2-polyphosphate on growth and tissue vitamin C concentrations in juvenile olive flounder, Paralichthys olivaceus (Temminck et Schlegel)

This experiment was conducted to study the effects of different dietary levels of vitamin C, L‐ascorbyl‐2‐polyphosphate (ASPP), on growth and tissue vitamin C concentrations in juvenile olive flounder, Paralichthys olivaceus (Temminck et Schlegel). Fish were fed one of six semi‐purified diets containing an equivalent of 0, 25, 50, 75, 150, or 1500 mg ascorbic acid (AA) kg^?1 diet (C₀, C₂₅, C₅₀, C₇₅, C₁₅₀ or C₁₅₀₀) in the form of ASPP for 12 weeks. Weight gain (WG) and protein efficiency ratio (PER) of fish fed the C₀ diet were significantly lower than those of fish fed the other diets (P < 0.05), and WG and PER of fish fed the C₂₅, C₅₀ and C₇₅ diets were significantly lower than those of fish fed the C₁₅₀₀ diet (P < 0.05). Fish fed the C₀ diet exhibited vitamin C deficiency symptoms such as anorexia, scoliosis, cataract, exophthalmia and fin hemorrhage at the end of the 12‐week test. After 12 weeks of the feeding trial, AA concentrations from gill, kidney, and liver of fish fed the C₀, C₂₅, C₅₀ and C₇₅ diets were significantly lower than those of fish fed the C₁₅₀ and C₁₅₀₀ diets (P < 0.05). Based on broken line analyses for WG and PER, the optimum dietary levels of vitamin C were 91 and 93 mg AA kg^?1 diet respectively. These findings suggest that the dietary vitamin C requirement could be 93 mg AA kg^?1 diet to support reasonable growth, and greater than 150 mg AA kg^?1 diet may be required for AA saturation of major tissues for juvenile olive flounder under experimental conditions.