Effects of dietary carbohydrate level on growth performance, innate immunity, antioxidant ability and hypoxia resistant of brook trout Salvelinus fontinalis

摘要

Juvenile brook trout were fed on six isonitrogenous and isolipidic diets, containing graded levels of gelatinized corn starch (50, 100, 150, 200, 250, 300 g/kg diet) for 81 days. Cellulose was used to compensate carbohydrate loss. The weight gain, specific growth rate and protein efficiency ratio increased as the dietary carbohydrate level increased from 50 to 150 g/kg, but decreased thereafter (p < .05). Quadratic regression analysis revealed that the optimum dietary carbohydrate level was in the range of 187.1-194.1 g/kg. In addition, serum alanine transaminase and aspartate transaminase activities, as well as glucose content, were highest in the group fed on 300 g/kg carbohydrate (p < .05). The hepatic malondialdehyde level increased with dietary carbohydrate levels (p < .05). The hepatic lysozyme activity increased as dietary carbohydrate level increased from 50 to 150 g/kg and decreased thereafter (p < .05). The overall survival rate after hypoxia challenge (45 min; dissolved oxygen content: 2.2 mg L-1) decreased with dietary carbohydrate levels (p < .05). Taken together, these results suggested that optimal level of dietary carbohydrate could improve growth performance. However, excessive dietary carbohydrate intake (> 250 g/kg) may decrease innate immunity status, increase oxidative stress and reduce resistance to hypoxia stress in brook trout.