Evaluation of muscle quality and movement-related traits in two common carp strains under a rice–fish farming system

In order to select the fish varieties that are suitable for rice–fish system in terms of nutrition and field adaptability, we compared the muscle characteristics between two common carp varieties, namely, the Congjiang strain (CJ) and FFRC No. 2 strain (FR) to illustrate their nutrition and movement differences when farmed in the paddy field. The nutritional composition analysis of muscles revealed that the protein content of FR was significantly higher than that of CJ (P < 0.01). Conversely, the fat content of CJ was significantly higher than that of FR (P < 0.01). Both varieties contained 16 amino acids and 21 fatty acids. The essential amino acid index of FR was higher than that of CJ. The contents of n-3 and n-6 fatty acids in CJ muscle were significantly higher than those in FR muscle (P < 0.05). Muscle texture and structure analysis showed that FR exhibited significantly higher hardness, chewiness, gumminess, and resilience than CJ (P < 0.01). Additionally, CJ had significantly smaller muscle fiber diameter and area than FR (P < 0.01). However, CJ displayed significantly higher muscle fiber density than FR (P < 0.01). Finally, the fluorescence detection results showed that the content of reactive oxygen species (ROS) in FR muscle cells was significantly higher than that in CJ muscle cells (P < 0.01). The results indicated that both carp varieties were excellent sources of protein and fat, with reasonable amino acid composition and rich beneficial fatty acid content. The muscle characteristics affected movement capacity of fish. It is conceived that the crossbreed of these two varieties may be a promising variety for the rice–fish symbiosis system because it could provide more favorable nutrition and overcome the shortage of each parent fish (low growth rate in CJ and high escape potential in FR).