Effects of dietary lipid and protein levels on growth, body composition, antioxidant capacity, and flesh quality of mandarin fish (Siniperca chuatsi)

The present study explored the effects of dietary lipid and protein levels on growth performance, body composition, antioxidant capacity, and flesh quality of mandarin fish ( Siniperca chuatsi ). Nine experimental diets containing graded levels of crude lipid (8%, 12%, and 16%) and crude protein (45%, 50%, and 55%) were formulated in a 3 × 3 factorial design. Eight hundred and ten mandarin fish (mean initial body weight, 20.90 ± 0.02 g) were randomly assigned into 27 tanks (1000 L) and triplicate tanks of fish were fed one of the experimental diets twice daily for 56 days. The results showed that a 16% dietary lipid level could significantly increase the survival rate of cultured fish, while a 55% dietary protein level could significantly increase the final body weight and specific growth rate of mandarin fish. Additionally, there was a significant interaction between dietary lipid and protein levels in terms of feed intake and protein digestibility. Further, the whole body and liver lipid content of cultured fish significantly increased with the increase of dietary lipid level, while the provision of dietary protein level significantly decreased the liver crude lipid content, and there was a significant interaction between dietary lipid and protein levels on the moisture, protein, and lipid content of the liver of cultured fish. In terms of hepatic antioxidant capacity, the total anti-oxidative capacity and the activities of catalase and superoxide dismutase decreased significantly with increasing dietary lipid or protein content. As to flesh quality, muscle hardness, chewiness, gumminess, and shear increased significantly with decreasing muscle lipid content, which is significantly influenced by dietary lipid content. In conclusion, considering all the results, the appropriate levels of lipids and protein in the diet for mandarin fish were 12% and 50%, respectively. This study provided reliable experimental data and theoretical basis for both subsequent research and the application of artificial compound feed for mandarin fish. Graphical Abstract