Bioeficácia da suplementação de metionina sintética em dietas para juvenis do camarão litopenaeus vannamei

Abstract

The present study aimed at comparing the bioefficacy of diets supplemented with two sources of synthetic methionine, DL-Methionine and DL-Methionyl-DL-Methionine in diets for the juvenile Pacific white shrimp, Litopenaeus vannamei. Eight treatments were evaluated, varying the free methionine source (DL-Met and Met-Met), and supplementation levels (0.10, 0.19, 0.29, 0.38% on a dry matter basis for DL- Met and 0.11, 0.20, 0.30, 0.39% on a dry matter basis for Met-Met). A diet without methionine supplementation, was used as a control with a total dietary methionine content of 0.43% originating only from intact sources. Shrimp were reared for 63 days, in 50 tanks of 0.5 m3, operating under a continuous water recirculation regime, at a rate of 20% per day, without filtration. Shrimp final body weight was maximized with DL-Met and Met-Met supplemented at 0.19% and 0.20%, equivalent to 0.66% and 0.64% of total dietary methionine (1.11% and 1.02% methionine + cystine), respectively. The present study demonstrated that diets supplemented with both sources of crystalline methionine lead to an increase in shrimp growth performance when compared to a diet without supplementation. No statistical differences were observed on the shrimp growth performance between diets supplemented with DL-Met and Met-Met. However, the level of dietary supplementation and the source of crystalline methionine affected the protein and amino acid composition of the caudal muscle and the digestive gland of shrimp. Higher supplementation levels using Met-Met lead to a higher content of crude protein, essential and non-essential amino acids, in particular methionine, lysine and cystine, in the digestive gland and in the caudal muscle of shrimp.