Effect of Dietary Methionine on Taurine Distribution and Non-specific Immune Responses in Juvenile Blunt Snout Bream, Megalobrama amblycephala at A Constant Dietary Cystine Level
Israeli Journal of Aquaculture (Bamidgeh)
Published by the The Society of Israeli Aquaculture and Marine Biotechnology (SIAMB) in partnership with the University of Hawaii at Manoa Library and the AquacultureHub A non-profit organization 501c3 Abstract A 9-week feeding trial was conducted to investigate taurine distribution by supplementation of methionine in juvenile Megalobrama amblycephala at a constant dietary cystine level. Six semi-purified diets were formulated to contain graded dietary methionine levels from 0.39-1.54% in about
... 0.39-1.54% in about 0.25% increments. At the end of feeding trial, plasma methionine content significantly increased with increasing dietary methionine level from 0.39 to 1.0% (P < 0.05) and thereafter reached a plateau. The taurine content of muscle, intestine, liver, and eye in the fish fed dietary methionine level ranged from 1.24-1.54% and was significantly higher than that of the control group (P < 0.05). Taurine content of the brain in fish fed 1.54% methionine diet was higher than the fish fed 0.39% (P < 0.05). Cysteine sulfinic acid decarboxylase content significantly increased with increasing dietary methionine level from 0.39-0.85% (P < 0.05) and thereafter stayed at a similar level. Supplementation with methionine significantly increased (P < 0.05) plasma total protein (TP) content, complement 3 (C3) content and superoxide dismutase (SOD) activity (0.85% methionine diet groups), aspartate transaminase (AST) activity (1.24% methionine diet groups) and albumin content (1.0% methionine diet groups). Supplemented groups had significantly decreased plasma urea content (0.85% methionine diet groups) (P < 0.05). In conclusion, these results indicate that crystalline methionine can be utilized efficiently, juvenile blunt snout bream were able to convert methionine to taurine directly, and appropriate dietary methionine supplementation improves non-specific immune responses in blunt snout bream.