Dietary lysine requirement of juvenile Pacific white shrimp, Litopenaeus vannamei

Abstract

An 8-week feeding trial was conducted to estimate the dietary lysine requirement of juvenile Pacific white shrimp, Litopenaeus vannamei. Six isonitrogenous and isolipidic practical diets (40% CP and 7.5% lipid) containing graded dietary lysine levels ranged from 1.44 to 2.49% (dry weight) at about 0.3% increments were formulated. Equal amino acid nitrogen was maintained by replacing lysine with nonessential amino acid mixture. Triplicate groups of 40 juvenile shrimps (about 0.52g initial weight) were fed one of the diets four times daily to apparent satiation. No significant differences were observed in survival rates of shrimps (97.50–100%, P>0.05), but specific growth rate (SGR), weight gain (WG), feed efficiency, protein efficiency ratio and protein deposition ratio were significantly affected by different dietary lysine levels (P<0.05). There were no significant differences in whole body and muscle composition (crude lipid, crude protein and ash), except for the crude protein content of whole body. Urea nitrogen, total protein and the activity of SOD in hemolymph showed no significant differences (P>0.05). Triglyceride, Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) in hemolymph were significantly affected by dietary lysine levels (P<0.05). The optimal dietary lysine requirement estimated by broken-line model based on SGR was 2.05% of dry diet (4.93% dietary protein). Considering the lysine leaching loss in seawater within 30min (duration of feeding each time), the lysine requirement for L. vannamei is 1.64% of dry diet (3.95% of the dietary protein).