Abstract
The study investigated the effect of replacing soybean meal with faba bean in practical diets on growth performance, meat quality, intestinal microbiota, and muscle transcriptomics of Litopenaeus vannamei. In a practical feed with fish meal, soybean meal, and flour contents of 200, 250, and 250 g/kg (control group, FB0), 150, 300, and 450 g/kg of faba bean were used to substitute 30%, 60%, and 90% of the dietary soybean meal-flour mixture (1:1; FB15, FB30, and FB45). Thus, the contents of soybean meal and flour were reduced to 175, 100, and 25 g/kg, respectively, to form four isonitrogenous feeds. Shrimp with an initial body mass of 1.40 ± 0.07 g were fed with the above four feeds for 8 weeks. All four groups presented no significant difference in growth performance, including weight gain (WG), feed conversion ratio, feed intake, and protein efficiency ratio. When faba bean inclusion reached 300 g/kg (FB30 and FB45 groups), the total free amino acid and free flavor amino acid contents in flesh were significantly increased (p < 0.05), and the boiling loss in the FB30 group, the steaming loss, and the boiling loss in the FB45 group were significantly lower than those of the control group (p < 0.05). The flesh hardness and chewing of the FB45 group were also significantly higher than those of the control group (p < 0.05). When faba bean inclusion reached 450 g/kg, the abundance of intestinal Proteobacteria and Actinobacteriota was decreased, while the abundance of Firmicutes was increased. In addition, the high inclusion of faba bean promoted the expression of related pathways such as myosin and myogenic fibers, as well as the genes such as fibrillin-2 (FBN2), troponin C (TnC), and myosin regulatory light chain 2 (MRLC2). In conclusion, high dietary inclusion of faba bean improved the meat quality and almost completely replaced soybean meal without negative effects on the growth of Pacific white shrimp.