Effects of different dietary binders on growth, body composition, intestinal barrier and target of rapamycin pathway of juvenile largemouth bass (Micropterus salmoides)

An 8-week experiment was conducted to explore the effects of dietary binder sources on juvenile largemouth bass (initial body weight: 32.00 ± 0.10 g). Five isolipidic diets were designed, supplementing with different binder sources: sodium alginate (SA), carrageenan (CG), hydroxypropyl methyl cellulose (HPMC), gelatin (GT), and starch (SC). Each diet was fed to triplicate groups with 30 fish in each group twice daily. The results showed that dietary inclusion of GT significantly improved the growth performance of cultured fish. Meanwhile, the protein efficiency ratio in the GT group was significantly higher than that of other groups, while the feed conversion rate in GT group was significantly lower than that of other groups. Gene expression analysis showed that SA, CG and GT inclusion up-regulated the expression of claudin-1 and claudin-4 compared to other groups. The expression of mucin 2 (muc2) in the GT group was significantly higher than that in HPMC group and SC group, and the highest expression of occluding was also observed in this group. In addition, the relative expression levels of target of rapamycin (tor), protein kinase B α (akt1) and S6 kinase beta-1 isoform l (s6kβ1) in SA, CG and GT groups were higher compared to the other two groups. Meanwhile, the relative expression of ribosomal protein S6 (s6) in the GT group was significantly higher than HPMC and SC groups. In summary, in this experiment, consider the results on growth performance and intestinal barrier function, GT was the appropriate binder for juvenile largemouth bass.