An 8-week experiment was performed to investigate the influence on growth performance, plasma biochemistry, glucose metabolism and the insulin pathway of supplementation of dietary taurine to a high-carbohydrate diet for grass carp. In this study, fish were fed diets at one of two carbohydrate levels, 31·49 % (positive control) or 38·61 % (T00). The high-carbohydrate basal diet (T00), without taurine, was supplemented with 0·05 % (T05), 0·10 % (T10), 0·15 % (T15) or 0·20 % (T20) taurine, resulting in six isonitrogenous (30·37 %) and isolipidic (2·37 %) experimental diets. The experimental results showed that optimal taurine level improved significantly weight gain, specific growth rate (SGR), feed utilisation, reduced plasma total cholesterol levels, TAG and promoted insulin-like growth factor level. Glucokinase, pyruvate kinase and phosphoenolpyruvate carboxykinase activities showed a quadratic function model with increasing dietary taurine level, while hexokinase, fatty acid synthetase activities exhibited a positive linear trend. Optimal taurine supplementation in high-carbohydrate diet upregulated insulin receptor (Ir), insulin receptor substrate (Irs1), phosphatidylinositol 3-kinase (pi3k), protein kinase B (akt1), glycogen synthase kinase 3 β (gs3kβ) mRNA level and downregulated insulin-like growth factor (igf-1), insulin-like growth factor 1 receptor (igf-1R) and Fork head transcription factor 1 (foxo1) mRNA level. The above results suggested that optimal taurine level could improve growth performance, hepatic capacity for glycolipid metabolism and insulin sensitivity, thus enhancing the utilisation of carbohydrates in grass carp. Based on SGR, dietary optimal tributyrin taurine supplementation in grass carp was estimated to be 0·08 %.

The essential role of taurine in the diet of the cat has been well documented and a deficiency of this nutrient is known to be responsible for a number of clinical conditions. At present, the National Research Council (1986) recommendation for the minimum dietary requirement of the kitten is 400 mg/kg dry matter and for a pregnant cat is 500 mg/kg dry matter. However, these minima were established by feeding the animals on semi-purified diets and, therefore, may be inappropriate for other dietary regimens. The aim of the present study was to investigate the effect of feeding a series of specially prepared diets containing different concentrations of taurine (canned diets 1475–5750 mg/kg dry matter, dry diets 811–1240 mg/kg dry matter) on the plasma taurine concentration of the cat. All diets were fed solus for 6 weeks and plasma taurine concentration was measured every 2 weeks. The results showed that to maintain plasma taurine values in the ‘normal’ range (> 60 μmol/l), a canned diet must supply at least 39 mg taurine/kg body-weight per d and a dry diet at least 19 mg/kg body-weight per d; a cat fed on a semi-purified diet need only achieve a daily intake of at least 10 mg taurine/kg body-weight to maintain an adequate circulating level of taurine. The cause of the reduced availability of taurine from these diets is not yet known. Furthermore, repletion of plasma concentration above 60 μmol/l can be achieved within 2 weeks of feeding an adequate diet.