Dietary Sodium Butyrate Improves Intestinal Health of Triploid Oncorhynchus mykiss Fed a Low Fish Meal Diet

Abstract

This study aimed to determine the effects of dietary sodium butyrate (NaB) on the growth and gut health of triploid Oncorhynchus mykiss juveniles (8.86 ± 0.36 g) fed a low fish meal diet for 8 weeks, including the inflammatory response, histomorphology, and the composition and functional prediction of microbiota. Five isonitrogenous and isoenergetic practical diets (15.00% fish meal and 21.60% soybean meal) were supplemented with 0.00% (G1), 0.10% (G2), 0.20% (G3), 0.30% (G4), and 0.40% NaB (G5), respectively. After the feeding trial, the mortality for G3 challenged with Aeromonas salmonicida for 7 days was lower than that for G1 and G5. The optimal NaB requirement for triploid O. mykiss based on weight gain rate (WGR) and the specific growth rate (SGR) was estimated to be 0.22% and 0.20%, respectively. The activities of intestinal digestive enzymes increased in fish fed a NaB diet compared to G1 (p < 0.05). G1 also showed obvious signs of inflammation, but this inflammation was significantly alleviated with dietary NaB supplementation. In comparison, G3 exhibited a more complete intestinal mucosal morphology. Dietary 0.20% NaB may play an anti-inflammatory role by inhibiting the NF-κB-P65 inflammatory signaling pathway. Additionally, the relative abundance of probiotics was altered by dietary NaB. In conclusion, dietary 0.20% NaB improved the intestinal health of triploid O. mykiss fed a low fish meal diet.