Supplementations of dl‐Methionine and Methionine Dipeptide in Diets are Effective for the Development and Growth of Larvae and Juvenile Red Sea Bream, Pagrus major

Growth trials for larvae and juvenile red sea bream, Pagrus major, were conducted to elucidate the efficacy of two molecular forms of methionine; dl-methionine (dl-Met) and methionine dipeptide (Met-Met). For the larvae experiment, five experimental diets were formulated and fed to fish (42 mg) for 30 days. A diet which has 15% soy protein isolate served as the control diet. Similarly, test diets supplemented with dl-Met and Met-Met at 0.5%, which were either precoated by zein or intact, were also formulated. For the juvenile experiment, five experimental diets were formulated wherein the control diet contained 25% soy protein isolate. Test diets were supplemented with dl-Met and Met-Met at 0.75%, which were either coated by carboxymethycellulose or intact and fed to juveniles (0.75 g) for 56 days. The results of two feeding trials showed both dl-Met and Met-Met can be equally utilized by red sea bream larvae and juveniles. Coating the amino acid significantly improved both fish larval and juvenile growth performance. The development of digestive protease activity of larvae was significantly influenced by coating the amino acid, but the type of methionine was not a factor in changing the protease activity of larvae.