Increasing feed allowance in low-fish meal diets allows for a reduction in dietary methionine for juvenile Litopenaeus vannamei raised in green-water tanks

Abstract

A 10-week study was conducted to evaluate the effect of feed allowance and graded levels of dietary methionine (Met) on growth performance of Litopenaeus vannamei. Juvenile shrimp of 1.83±0.14 g were stocked in 42 outdoor green-water tanks of 1 m 3 under 120 shrimp m −2. Animals were fed under two feed allowances, regular and 30% in excess. Five diets with 30 g kg −1 fishmeal were designed to contain 318±2 g kg −1 crude protein and a minimum amount of protein-bound Met. To achieve graded levels of dietary Met, a control diet with 4.6 g kg −1 Met or 8.9 g kg −1 methionine + cysteine (M+C) was supplemented with 1.2, 2.2, 3.2, and 4.2 g kg −1 of DL-methionyl-DL-methionine to result in total dietary Met of 5.6, 6.9, 7.9, and 9.2 g kg −1 (10.0, 11.2, 12.1, and 13.5 g kg −1 M+C, respectively). A final survival of 86.5±3.6% was reached with no significant influence from feed allowance or dietary Met. Feed inputs significantly affected apparent feed intake, weekly shrimp growth, final body weight (BW), and gained yield. Larger meals and a higher dietary Met had no impact on feed conversion ratio. There was a significant interaction between feed allowance and Met over shrimp BW. By feeding animals in excess, BW was enhanced at 6.9 g kg −1 Met. A dietary Met of 7.9 g kg −1 was required to achieve a maximum BW under a regular feed allowance. Thus, shrimp required less amounts of dietary Met to maximize BW when higher feed inputs were delivered. Our findings demonstrate a sparing effect of dietary Met for L. vannamei when a higher feed allowance is adopted. Shrimp farmers should consider adjusting feed allowance to dietary Met to maximize shrimp growth performance and yield.

Optimal Levels of Fish Meal and Methionine in Diets for Juvenile Litopenaeus vannamei to Support Maximum Growth Performance with Economic Efficiency

“…For the growth performance evaluation, an outdoor rearing system as described by Façanha et al [50][51][52] and Nunes et al [54] was used. The system consisted of independent 1.0 m 3 outdoor tanks (1.02 m 2 bottom area × 0.74 m height), each equipped with a perforated lid on the top to avoid shrimp from escaping.…”

“…Methionine (Met) is considered the most impacted essential amino acid (EAA) when fish meal is challenged. Recommended dietary Met levels in shrimp feeds have ranged between 0.7% and 1.0% of the diet (as-fed basis) depending on shrimp species (Penaeus monodon [43], Marsupenaeus japonicus [44]), source of supplemental Met [13,20,[45][46][47][48], growth stage [49], culture conditions (stocking density [50], water exchange regime [51], feed allowance [52]), and dietary protein level [53,54]. However, very little information is available on the optimal dietary Met levels in response to graded levels of fish meal in order to support maximum shrimp growth performance with economic efficiency.…”