Objective The present study aims to evaluate the effects of different proportions of dietary mulberry leaf powder (MLP) on the growth performance, meat quality and flavor of grass carp in order to provide a theoretical basis for the application of MLP in aquaculture.

Method Five isonitrogenous (including 25.55% of protein and 3.25% of isolipid) diets respectively supplemented with 0(control), 5%, 10%, 15% and 20% MLP were prepared.A total of 1 500 grass carp (initial body weight=1 112.06±83.19 g) were randomly assigned to five dietary treatment groups and fed for 8 weeks.

Result Compared with the control group, the grass carp supplemented with 10% MLP in the diets had significantly higher values of the viscera somatic indexes.However, the supplementation of all proportions of MLP showed no significant effect on the final body weight, weight gain rate, specific growth rate, feed conversion ratio, survival rate, hepatopancreas somatic index and condition factor of grass carp.Supplementation of 5% MLP in the diets could significantly improve the hardness, gumminess, chewiness and resilience of the muscles, but had no significant effect on the springiness, cohesiveness and shear force of the muscles.Dietary supplementation of 10%, 15% and 20% MLP significantly reduced the cohesiveness of grass carp muscle, but showed no significant effect on the hardness, springiness, gumminess, chewiness and shear force of the muscles.In addition, both the compositions and contents of nutrients and flavor compounds in the muscles of experimental grass carp were analyzed.The results showed that the supplementation of 10% MLP in the diets significantly increased the contents of proteins, fat, delicious amino acids, flavor amino acids, essential amino acids, semi-essential amino acids, total amino acids, inosinic acid, unsaturated fatty acids and monounsaturated fatty acids, while significantly reduced the content of polyunsaturated fatty acids in grass carp muscles.The contents of the above nutrients and flavor compounds were also partially increased in other MLP groups.

Conclusion The supplementation of no more than 20% MLP in the diet does not significantly affect the growth performance of grass carp, but can obviously increase the contents of proteins, inosine monophosphate, flavor amino acids and unsaturated fatty acids in the muscles as well as improve the meat quality and flavor of grass carp.