Effects of graded levels of histidine on growth performance, digested enzymes activities, erythrocyte osmotic fragility and hypoxia-tolerance of juvenile grass carp Ctenopharyngodon idella

The present study determined optimum dietary histidine requirement for juvenile grass carp and the data goes to 1.21% of the diet, corresponding to 3.2% of dietary protein. We also found that juvenile grass carp fed with histidine deficiency diet not only limited their growth performance, but also exhibited higher erythrocyte osmotic fragility, lower hypoxia-tolerance and antioxidant enzyme activities. Digested enzyme activities were also significantly affected by the dietary histidine levels. Thus, it is important to meet histidine requirement when commercial diets are formulated for this species.