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This study was conducted to investigate the mechanism of green liver symptom induction and the effect of dietary taurine supplementation on growth performance in juvenile red sea bream fed non-fishmeal diets based on soy protein concentrate (SPC). Juvenile fish (initial BW 72 g) were fed for 20 weeks on SPC diets supplemented with taurine at levels of 0, 1.0, and 2.0%. In the taurine-unsupplemented SPC diet group, specific growth rate (SGR) and feed conversion ratio (FCR) were significantly inferior ( P < 0.001), and incidence of green liver was observed in 70% of fish. In this group, hepatopancreatic and plasma taurine concentrations were lowest ( P < 0.05), hepatopancreatic content of bile pigments was highest ( P < 0.05), and osmotic tolerance of erythrocytes was inferior ( P < 0.05) among the dietary treatment groups. Serum osmolality of all treatment groups was at similar levels. These physiological abnormalities as well as SGR and FCR were improved by dietary taurine supplementation. These results indicate that the mechanism for induction of green liver symptom is bile pigment overproduction due to increased hemolysis because erythrocytes become osmotically fragile due to dietary taurine deficiency. Taurine supplementation of SPC diets is essential for maintaining normal physiological condition and growth performance in juvenile red sea bream. [ABSTRACT FROM AUTHOR]

The necessity of dietary taurine supplementation for preventing green liver symptom and improving growth performance of red sea bream Pagrus major fed nonfishmeal (non-FM) diets was investigated. Yearling red sea bream (initial body weight, 580 g) were fed for 36 weeks on non-FM diets based on soy protein concentrate (SPC) supplemented with taurine at levels of 0%, 0.5%, 1.0%, 1.5%, and 2.0%. Specific growth rate (SGR) and feed conversion ratio (FCR) of fish fed the taurine-unsupplemented SPC diet were markedly inferior. In these fish, incidence of green liver was markedly higher and was accompanied by a decrease of tissue taurine concentration and an increase of hepatopancreatic bile pigment content. The green liver symptom was mainly caused by an increase of hemolysis since the erythrocytes became osmotically fragile due to taurine deficiency. Physiological abnormality and growth performance (SGR and FCR) were markedly improved by taurine supplementation to the SPC diets. These results indicate that dietary taurine supplementation is necessary for yearling red sea bream fed non-FM diet based on SPC to maintain normal physiological condition and growth performance. [ABSTRACT FROM AUTHOR]