Effects of faba beans (Vicia faba L.) on muscle texture and fibrosis biomarkers of Nile tilapia (Oreochromis niloticus)

Crispy Nile tilapia (<i>Oreochromis niloticus</i>) is a valuable fish with high muscle hardness and chewiness, generated by feeding the fish with faba beans (<i>Vicia faba L.</i>). Reactive oxygen species (ROS) stress response may be one of the physiological causes responsible for the crispy change in muscle texture. However, molecular mechanisms controlling fish muscle texture particularly those arising from faba beans in the diet are unclear. In this study, Nile tilapia was fed with faba beans or commercially formulated feed lacking faba beans for 80 days. Thereafter, fish samples were examined for muscle texture, microstructure, collagen content and transcriptome to determine the mechanism of formation of crisp muscle texture. The results showed muscle texture indexes (hardness, resilience, gumminess, and chewiness) increased, muscle fibre diameter decreased as density increased, and the amount of total collagen in the extracellular matrix of muscle increased significantly in the faba bean-fed group. The expression of genes associated with fibrosis (<i>col1α1</i>, <i>versican</i>, <i>comp</i> and <i>fibrosin</i>) were significantly upregulated, while that of <i>decorin</i>, which is known to inhibit fibrosis, was downregulated in the faba bean-fed group. Overall, our study founded that feeding tilapia with faba beans can change muscle textural quality by altering the muscle fibres and collagen content. We also identified genes which induce changes in fibrosis of muscle that are related to the improved textural quality in crisp tilapia, providing theoretical guidance for the regulation of crispy tilapia.