Influence of dietary phosphorus on growth performance, phosphorus accumulation in tissue and energy metabolism of juvenile swimming crab (Portunus trituberculatus)

Abstract

Abstract An 8-weeks feeding trial was conducted to evaluate the effects of different dietary phosphorus (P) levels on growth performance, P concentrations in tissue, haemolymph biochemistry and hepatopancreatic metabolic enzyme activities for juvenile swimming crab (Portunus trituberculatus). Five semi-purified diets (46 % protein, 7.5 % lipid) were formulated to contain different P levels of 6.4, 10.8, 16.2, 21.0 and 25.7 g kg−1, respectively. Each diet was randomly assigned to triplicate groups of 30 juvenile swimming crab (initial weight was 12.82 ± 0.15 g) that were reared in single crab unit. The results indicated that percent weight gain (PWG) were significantly influenced dietary P levels, the highest PWG were observed in crabs fed the diet containing 16.2 and 21.0 g kg−1 P. Moreover, P contents in muscle, hepatopancreas and carapace significantly increased with dietary P levels increasing from 6.4–21.0 g kg−1. P retention rate (PRR) in hepatopancreas and muscle significantly decreased with dietary P levels increasing from 6.4 to 25.7 g kg-1. Furthermore, dietary deficient P (such as 6.4 and 10.8 g kg−1 P) levels reduced ATP content, activities of PK and SDH in hepatopancreas. Crabs fed the diet with 6.4 g kg−1 P also showed significantly lower expression of genes involved in electron transport chain complex, such as nd1, sdhc and coxIII in hepatopancreas than those fed the other diets. The expression of genes related to mitochondrial energy metabolisms, such as Atpase6, sirt1, and nrf1 in hepatopancreas were significantly up-regulated in crabs fed 16.2 and 21.0 g kg−1 P diets. Overall, based on the two slope broken-line and quadratic regression analysis of PWG against the dietary total P levels, the optimum dietary P requirement was estimated to be 15.91 and 16.83 g kg−1, respectively.