Effect of dietary taurine on the growth, mitochondrial function, lipid metabolism, and muscle texture of coho salmon (Oncorhynchus kisutch)

In this study, the effect of graded dietary taurine levels on the growth performance, lipid metabolism, and muscle texture was investigated in coho salmon ( Oncorhynchus kisutch ). Six isonitrogenous and isolipidic diets were formulated with taurine levels at 0, 0.2, 0.4, 0.6, 0.8, and 1.0 g/kg. Juvenile coho salmon (∼ 8.2 g) were fed the experimental diets for 8 weeks. Dietary taurine deficiency (0 g/kg) resulted in poorer growth performance and higher hepatic lipid accumulation, accompanied by depressed mitochondrial function. Compared to the deficient group, dietary taurine at 0.2 ∼ 0.8 g/kg enhanced hepatic mitochondrial membrane potential and activities of mitochondrial respiratory chain enzyme complexes (I-IV). In addition, dietary taurine at 0.2 ∼ 0.8 g/kg reduced the activities and gene expression of lipogenic enzymes, but promoted the expression of β-oxidation genes, leading to lowered hepatic and serum lipid contents. Conversely, the excessive taurine supplementation at 1.0 g/kg failed to confer additional benefits, with most physiological parameters regressing to levels comparable to the deficient group. The quadratic regression analysis indicated the optimal dietary taurine level was 0.45 ∼ 0.49 g/kg for coho salmon based on the weight gain rate, specific growth rate, and feed conversion ratio. The metabolic optimization was accompanied by upregulated key genes in the mTOR pathway, improved muscle texture parameters, and elevated serum free amino acid levels. In conclusion, the optimal levels of dietary taurine promotes salmon growth by enhancing feed efficiency, lipid metabolism, and mitochondrial function in coho salmon.