Dietary leucine level affects growth performance, whole body composition, plasma parameters and relative expression of TOR and TNF-ɑ in juvenile blunt snout bream, Megalobrama amblycephala

Blunt snout bream, Megalobrama amblycephala, is a major cultured freshwater fish species in China, which has a long history of cultivation because of its excellent flesh quality, rapid growth performance and high larval survival rate. Its production has been rapidly increased and reached approximately 0.70 million tons in 2012. Economic fish production relies on low cost commercial diet development. However, there is no available data on dietary leucine requirement of blunt snout bream. Hence, a standard nutrient requirement study with 6 graded levels of leucine fed to 3 groups of fish for each diet was set up. The results showed that dietary leucine levels significantly influenced the growth performance, whole body composition, and relative expression of TOR and TNF-ɑ mRNA in juvenile blunt snout bream. Plasma leucine level significantly increased with increasing dietary leucine levels, while plasma isoleucine levels were enhanced in leucine deficient fish. The dietary leucine requirement of juvenile blunt snout bream was determined to be 1.44% of dry diet (4.24% of dietary protein) and 1.61% of dry diet (4.74% of dietary protein) on the basis of SGR and FER, respectively. It would be useful in developing EAA balanced commercial feeds for juvenile blunt snout bream.