Effects of supplemental coated or crystalline methionine in low-fishmeal diet on the growth performance and body composition of juvenile cobia Rachycentron canadum (Linnaeus)

Abstract

We evaluated the effects of supplemental coated and crystalline methionine (Met) on the growth performance and feed utilization of juvenile cobia (Rachycentron canadum Linnaeus) in a 60-d feeding trial. Fish groups were fed one of six isonitrogenous and isolipidic diets: 1) fishmeal control; 2) un-supplemented experimental (low-fish-meal diet deficient in Met); or 3) one of four Met diets supplemented with crystalline L-Met, cellulose-acetate-phthalate coated L-Met, acrylic-resin coated L-Met, or tripalmitin-polyvinyl alcohol coated L-Met. The test diets were fed to triplicate groups of cobia (initial body weight 5.40±0.07 g) twice a day. The weight gain and specific growth rate of the fish fed the RES diet were highest among the Met-supplemented groups and were 23.64% and 7.99%, respectively, higher than those of the fish fed with the un-supplemented experimental diet (P<0.05). The protein efficiency ratio of the fish fed the MET diet was significantly higher than that of the fish fed the un-supplemented experimental diet and the fish in the other methionine supplementation groups (P<0.05). Our results suggest that supplementation of crystalline Met in low-fish-meal diets promotes the growth performance of juvenile cobia.