Effects of dietarydl‐methionyl‐dl‐methionine (Met‐Met) on growth performance, body composition and haematological parameters of white shrimp (Litopenaeus vannamei) fed with plant protein–based diets

Abstract

A 10-week feeding trial was conducted to evaluate the effects of supplementing different levels of dl-methionyl-dl-methionine (AQUAVI® Met-Met) in plant protein–based diets on Litopenaeus vannamei. The positive control (PC) and negative control (NC) diets were designed with 20% and 8% fishmeal respectively, and other six diets were formulated with graded levels of Met-Met from 0.05% to 0.30% with a 0.05% increment on the basis of NC diet (MM 0.05–MM 0.3). Six replicates were randomly assigned to each diet with 50 shrimp each having initial weight of 0.98 ± 0.02 g. The variation of FM concentration from 20% to 8% and supplemented with graded levels of Met-Met did not affect the survival rate, feed conversion ratio, protein efficiency ratio, whole body and muscle proximate compositions (p > 0.05). However, diets with ≤0.20% Met-Met supplementation resulted in significantly increased weight gain and specific growth rate, after which both parameters reached plateau. Shrimp fed the NC diet showed significantly lower total essential amino acid (EAA) content in muscle (p < 0.05). Supplementation of Met-Met significantly improved apparent digestibility coefficients of dry matter, crude protein, lipid, phosphorus and EAAs (p < 0.05). Based on broken-line analysis, the methionine requirement for white shrimp was estimated to be 0.87% when using Met-Met as methionine source.