Dietary arginine requirement of juvenile Pacific white shrimp, Litopenaeus vannamei

Abstract

An 8-week feeding trial was conducted to evaluate the dietary arginine requirement of juvenile Pacific white shrimp, Litopenaeus vannamei. Six isonitrogenous and isolipidic practical diets (41% crude protein and 7.5% crude lipid) were formulated to contain graded dietary arginine levels ranging from 1.44 to 2.74% (dry weight) in approximately 0.3% increments. In all of the diets, the nitrogen content of the amino acids was kept the same by replacing arginine with a non-essential amino acid mixture. Each diet was randomly assigned to triplicated groups of 40 juvenile shrimp (approximately 0.50g) 4 times daily to apparent satiation. The results indicated that the specific growth rate and weight gain were significantly influenced by the dietary arginine levels. Maximal specific growth rate and weight gain occurred at 2.32% dietary arginine; however, specific growth rate and weight gain did not significantly increase with further increases in dietary arginine from 2.51% to 2.74%. Feed efficiency, protein efficiency ratio and protein productive value were also significantly affected by the dietary arginine levels, and the trends were similar to those of growth performance. No mortality was observed among all treatments. There were no significant differences among crude protein, crude lipid and ash content in the whole body and muscle composition. The total protein in hemolymph was significantly affected by dietary arginine levels, however, there were no significant differences in urea nitrogen, triglycerides and cholesterol in the hemolymph among all treatments. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), superoxide dismutase (SOD), arginase and nitric oxide synthase (NO) activities in the hemolymph were significantly affected by dietary arginine levels. The optimal dietary arginine requirement estimated by two slope broken-line model based on SGR was 2.32% of the dry diet (corresponding to 5.66% of dietary protein on a dry weight basis). Considering the arginine leaching loss in seawater within 30min (duration of feeding each time), the arginine requirement for L. vannamei is 1.96% of dry diet (4.77% of the dietary protein).