Pomelo (Citrus grandis) peel and soybean meal co-fermented protein improved immune response and intestinal health, but not growth performance in largemouth bass (Micropterus salmoides)

• DOI: 10.1016/j.aqrep.2025.102660
• Publication Date: 2025-01-31T17:15:14Z
• Authors: Jian-Ming Xu; Zhuan-Zhuan Zhao; Ping Liang; Zhi Chen; Guo-He Cai; Hong-Ling Yang; Kang-Le Lu; Jian-Bin Lin; Yun-Zhang Sun
• Keywords: Citrus grandis peel; Fermented protein; Intestinal health; Immunity; Aquaculture. Fisheries. Angling; SH1-691; Largemouth bass

The present study aimed to assess the influence of pomelo (Citrus grandis) peel and soybean meal co-fermented protein (CFP) on growth performance, feed utilization, immune response, as well as hepatic and intestinal health in largemouth bass (Micropterus salmoides). Fish weighing 5.80 ± 0.01 g were allocated into five groups and given diets containing 0 %, 5 %, 10 %, 15 % and 20 % CFP for a duration of eight weeks. The growth performance and dietary utilization were not influenced by the supplementation of 5 %, 10 % and 15 % CFP. Otherwise, the total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activity were slightly improved by 5 %, 10 %, and 15 % CFP, while the malondialdehyde (MDA) content was reduced. Simultaneously, elevated alkaline phosphatase (AKP) activity and immunoglobulin M (IgM) content in groups with 5 % and 10 % CFP (P < 0.05). The intestinal barrier function was enhanced in groups containing 5 % and 10 % CFP, which is evidenced by the reduction in serum diamine oxidase (DAO) activity and the increased expression of intestinal Claudin-1 and ZO-1. Nevertheless, the inclusion of 20 % CFP damaged the development of villi and muscle, and inhibited the expression of Occludin. The intestinal pro-inflammatory cytokines (TNF-α, IL-1β and IL-8) were downregulated while the anti-inflammatory cytokines (IL-10 and TGF-β) expression were upregulated in groups supplemented with 5 %, 10 % and 15 % CFP. The expression of intestinal immune effector LYZ was significantly up-regulated in the group with 10 % CFP. Furthermore, the incorporation of 10 % CFP was found to effectively remodel the intestinal microbiota, as evidenced by an augmentation in the relative abundance of beneficial Firmicutes and a concurrent decrease in the abundance of potentially pathogenic Proteobacteria. In conclusion, the 5 %, 10 % and 15 % inclusion level of CFP in diets is conducive to enhancing the immunity, hepatic and intestinal health of largemouth bass, without compromising it’s feeding and growth performance.