Dietary supplementation Eucommia ulmoides extract at relative low level affect the nutrition, flavor, and crispness of grass carp (Ctenopharyngodon idella) by gut bacterial mediation

To further illustrate mechanisms of faba bean mediating grass crap crispness based on reactive oxygen species (ROS) stress, and to explore the potential of Eucommia ulmoides serving as feeding additive in aquaculture, a series of experiments were performed under faba bean and E. ulmoides extract treatments. Muscle depolymer-ization and breakdown as well as fiber diameter decline were determined under faba bean and E. ulmoides extract treatments, together with antioxidant enzyme activities reduction, suggesting the inhibition effect of the two substances are responsible for grass crap crispness. Significant variations in amino acids and fatty acids were detected under faba bean treatments. Besides, gut microbiota was also governed by faba bean and participated in amino acids and fatty acids metabolism. These alterations could induce lipid peroxidation and collagen regen-eration, which in turn affect grass crap crispness. Our results are beneficial to deeply clarify the mechanism of faba bean mediating grass crap crispness.