REPLACEMENT OF DIETARY FISH MEAL BY RAPESEED MEAL AND COTTONSEED MEAL ON MUSCLE TEXTURE, HEALTH AND EXPRESSION OF MUSCLE-RELATED GENES IN YELLOW CATFISH (PELTEOBAGRUS FULVIDRACO)

This article aims to study the effect of rapeseed meal and cottonseed meal on the muscle quality and the expression of genes related to muscle fiber development after replacing part of the fish meal in the diets of yellow catfish (Pelteobagrus fulvidraco). Five groups of equal nitrogen and equal energy diets were designed in the experiment. The group containing 25% fish meal was used as the control diet (FM), and rapeseed meal and cotton meal were mixed 3﹕2 to replace 10%, 20%, 30% and 40% fish meal, and then set up four test groups as RM10, RM20, RM30 and RM40, respectively. The juvenile yellow catfish with an initial body weight of (2.38±0.02) g were fed with the above five diets for 8 weeks. The experiment showed that, compared with the fishmeal group, as the replacement level exceeded 10%, the crude protein and crude fat in the muscle of yellow catfish decreased significantly when the replacement level increased, but there was no significant difference in moisture and ash. In addition, the content of hydroxyproline in muscle also showed a downward trend. Among the muscle fibers of yellow catfish, the number with a diameter of ≥50 μm decreased when the replacement level reached 10%, while the number of fibers with a diameter of ≤20 μm showed an upward trend. At the same time, the replacement of plant protein sources will also have a certain impact on the muscle texture of yellow catfish. In addition, the mRNA levels of muscle fiber development-related genes myod, myog, and mrf4 gradually increased as the replacement level reached 10%, while the gene expression of myf5 and mstn did not show significance between the groups. The expression of TOR and S6K1 decreased as the replacement level increased, and the expression of 4E-BP1 increased as the replacement level increased. Therefore, this study show that use of the rapeseed meal and cottonseed meal to replace more than 10% of the fish meal in the diet of yellow catfish juveniles will damage the muscle growth and muscle quality.