Effects of different dietary protein levels on growth performance, muscle quality, digestive enzymes and non-specific immunity of Leuciscus waleckii

Objective This experiment aims to investigate the relationship between dietary protein levels and growth performance, muscle quality, and biochemical parameters in Amur ide (Leuciscus waleckii), and further determine the optimal dietary protein level for its growth conditions.

Methods In the experiment, 600 healthy L. waleckii with an average initial body mass of (49.42±5.39) g were selected and randomly divided into five groups, with three replicates in each group and 40 fish in each replicate. The crude protein content of each group was 25.68%, 29.84%, 34.52%, 39.04%, 43.12% of five groups of diets with the same fat content. The experiment period is 56 days, based on the growth performance indicators including survival rate (SR), weight gain rate (WGR), specific growth rate (SGR), feed conversion ratio (FCR), and condition factor (CF) of the experimental fish, as well as the proximate composition of muscle and relevant enzyme activities in the liver and intestine.

Results The results showed that the weight gain rate and specific growth rate of the test fish in the 34.52% group were significantly higher than those in the 25.68% group and the 29.84% group (P<0.05). The feed conversion ratio of the 43.12% group was significantly lower than that of the 25.68% group and the 29.84% group (P<0.05). The crude protein content of the 34.52% group was significantly higher than that of the 25.68% group, the 29.84% group and the 43.12% group (P<0.05). The crude fat content of the 43.12% group was significantly higher than that of the 29.84% group and the 34.52% group (P<0.05). The amylase activity in the intestinal tract of test fish in the 34.52% group was significantly higher than that in the 25.68% group, the 29.84% group and the 43.12% group (P<0.05). The lipase activity in the intestinal tract of the test fish in the 34.52% group was significantly higher than that in the other groups (P<0.05). The protease activity in the intestinal tract of test fish in the 43.12% group was significantly higher than that in the 25.68% group, the 29.84% group and the 34.52% group (P<0.05). The acid phosphatase of the test fish in the 34.52% group was significantly higher than that in the 25.68% group (P<0.05).

Conclusion The results show that through polynomial regression analysis of the relationship between the weight gain rate and the crude protein level in the dietary, it is concluded that the most suitable dietary protein level for the sub-adult growth stage of L. waleckii was 37.52%.