Abstract

Hybrid sturgeon ( Acipenser schrenckii ♀× Acipenser baerii♂ ) were fed with four isonitrogenous (approximately 43.0%) and isolipidic (approximately 13.6%) diets: FM-based diet (lysine control diet, LC diet), poultry by-product meal totally substitute diet (lysine low diet, LL diet), LL diet supplemented lysine to match the LC diet group level (lysine medium diet, LM diet) and LL diet supplemented lysine over the LC diet group level (lysine high diet, LH diet) for 8 weeks to determinate the effect of dietary lysine supplementation on growth performance, metabolism and immunity response. The results indicated that compared with control diet, LL diet led to depressed growth performance and feed utilization. Lysine supplementation had a significant effect on improving the growth performance and feed utilization. Moreover, LL diet also decreased the plasma-free amino acid concentration, nutrient content and mRNA expression level of IGF system and increased plasma immunity indexes and gene expression level of HSP70 than the control diet. LM diet had marked efficiency to eliminate the differential effects caused by lysine insufficiency. However, high-level lysine addition had undesirable effect on regulating the growth performance, feed utilization, plasma-free amino acid concentration, nutrient content, immunity indexes and gene expression level. Present study demonstrated that poultry by-product meal with lysine addition could totally substitute FM without adverse effects on growth performance, plasma AA concentration, nutrient content and immune response in hybrid sturgeon. Our results provide a solid evidence for using lysine to improve the body growth performance and metabolism in hybrid sturgeon.