Detoxified camellia seed cakes improve muscle qualityof grass carp (Ctenopharyngodon idella)

This study aims to assess the viability of detoxified camellia seed cake (CSC) as an unconventional feed component for grass carp ( Ctenopharyngodon idella ), and to examine its dose-dependent impacts on growth performance, physiological health, muscle quality, and myogenic gene expression. A 90-day feeding trial was conducted on grass carp (starting body weight: 194.50 ± 0.80 g) using five isonitrogenous and isoenergetic diets supplemented with varying quantities of detoxified CSC (0%, 1%, 3%, 5%, and 7%, dry weight basis). The findings indicated that 1% CSC food supplementation did not negatively impact growth performance. A 3% dietary inclusion level of detoxified CSC was identified as the threshold for inducing significant improvements in grass carp flesh quality. Although the introduction of CSC at levels ≥3% reduced feed efficiency and growth performance, it did not significantly affect the survival rate. Importantly, this level of CSC significantly improved muscle nutritional composition, increased the content of flavor-related amino acids and long-chain polyunsaturated fatty acids, and enhanced textural attributes. These improvements were associated with the upregulation of myogenic regulatory factors ( MyoG , Myf5 , MyoD ) and downregulation of myostatin genes ( MSTN1 , MSTN2 ). This offers a theoretical foundation and technical direction for the optimal utilization of the phytochemicals in CSC.