Effects of dietary serine addition to a high plant protein diet on growth performance, body composition, hepatosomatic histological structure and metabolism of taurine synthesis in juvenile turbot (<scp><i>Scophthalmus maximus</i></scp> L.)

A feeding trial was carried out to investigate the effects of dietary serine on feeding, growth, biochemistry composition, hepatosomatic histological structure and metabolism of taurine synthesis in turbot (Scophthalmus maximus L.) (2.0 ± 0.01 g) fed plant protein-based diets. A fishmeal-based control diet (DietFM) and another two isonitrogenous and isolipidic plant-based diets containing 0.0% (DietPP) and 3.0% (DietS-3%) serine were formulated and fed twice daily (06:30 and 18:30) to fish in triplicate groups for 9 weeks. Feed intake in fish fed DietS-3% was notably higher than that in fish fed DietPP (p < 0.05), and no significant difference was discovered between fish fed DietFM and fish fed DietS-3% (p > 0.05). No significant difference (p > 0.05) was found with the increase of dietary serine in final body weight, specific growth rate, weight gain rate, feed efficiency ratio, protein efficiency ratio and survival rate when a significant increase (p < 0.05) was detected in hepatosomatic index between fish fed DietFM and fish fed DietS-3%. A significant increase was detected from 0.0% to 3.0% serine inclusion in ash content (p < 0.05) when no significant difference was discovered between the DietPP group and the DietS-3% group in moisture, protein and lipid content (p > 0.05). A significant increase (p < 0.05) was found from 0.0% to 3.0% serine supplementation in diets in body tarinre content when hepatosomatic L-cysteinesulphinate decarboxylase activity, cysteamine dioxygenase activity, liver and serum taurine content (p > 0.05) in fish fed DietS-3% showed no obvious difference with those of fish fed DietPP (p > 0.05). The cellular morphology and cell stripes in liver of fish fed diets with 3% serine inclusion were closer to that of fish fed DietFM. Considering the results, 3% serine supplementation in a high plant protein diet significantly increased feeding, mineral accumulation, body taurine content of turbot and obviously improved hepatosomatic histological structure. It is inferred that serine in a taurine-deficient diet can probably convert to taurine to some degree in juvenile turbot, and the transformation differs with tissue distinction.