The effects of dietary extract of mulberry leaf on growth performance, hypoxia-reoxygenation stress and biochemical parameters in various organs of fish

Abstract The study explored the effects of extract of mulberry leaves (EML) on the growth performance and hypoxia-reoxygenation stress as well as biochemical parameters in various organs of crucian carp (Carassius auratus gibelio). The results indicated that dietary EML improved the growth of crucian carp. The appropriate concentration of EML for fish growth was estimated to be 46.93 g kg−1 diet. Moreover, dietary EML raised the digestive, absorptive and metabolic function by improving feed intake and alpha‐amylase, lipase, trypsin, alkaline phosphatase, glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase activities in hepatopancreas or intestine and decreasing plasma ammonia content, and respiratory function by increasing GOT activities in the branchiae and hemoglobin level in red blood cells of crucian carp. After 30 days feeding trial, crucian carp was treated with hypoxia-reoxygenation. The result showed that dietary EML improved hypoxia tolerance in crucian carp. The appropriate concentration of EML for hypoxia tolerance was estimated to be 57.21 g kg−1 diet. Hypoxia-reoxygenation stimulated the loss of partial digestive, absorptive, respiratory and metabolic function, reactive oxygen species (ROS) generation and cellular component oxidation in the digestive and respiratory organs, suggesting the ability of hypoxia-reoxygenation to induce oxidative lesion in fish. However, dietary EML reduced the oxidative lesion in a way of suppressing the production of ROS and oxidation of cellular component and elevating activities of enzymatic antioxidant and levels of non-enzymatic antioxidant in the digestive and respiratory organs of fish caused by hypoxia-reoxygenation. Therefore, EML can be utilized as an inhibitor of hypoxia-reoxygenation stress in fish.