Effects of dietary sodium butyrate on growth, digestive enzymes, body composition and nutrient retention-related gene expression of juvenile yellow catfish (Pelteobagrus fulvidraco)

An 8-week feeding trial was conducted to evaluate the effects of sodium butyrate (SB) on growth, digestive enzymes, body composition and nutrient retention-related gene expression of juvenile yellow catfish ( Pelteobagrus fulvidraco ). Five isonitrogenous and isolipidic diets (420 g/kg protein and 90 g/kg lipid) were formulated to contain 0 (control), 250, 500, 1,000 or 2,000 mg/kg SB. Triplicate groups of 40 fish (BW = 1.26 ± 0.01 g) per tank (300-L cylindrical fiberglass tanks) for each diet were fed to apparent satiation twice daily. Stomach, hepatopancreas and intestine samples were obtained for digestive enzymes activities analyses. A real-time quantitative PCR analysis was performed to determine the relative expression of target of rapamycin ( TOR ) and lipoprotein lipase ( LPL ) in the hepatopancreas and intestine. Fish fed the diets supplemented with SB at 500 and 1,000 mg/kg showed significantly higher specific growth rate and significantly lower feed conversion ratio compared to the control ( P < 0.05). Dietary SB inclusion did not alter activities of intestinal amylase, creatine kinase and sodium-potassium adenosine triphosphatase (Na + /K + -ATPase), but increased activities of hepatic trypsin, stomachic lipase, intestinal lipase, alkaline phosphatase and γ-glutamyl transpeptidase for fish fed 1,000 mg/kg SB compared to the control ( P < 0.05). Intestine length index, intestine somatic index, fold height and muscular thickness of distal intestine were significantly higher in 1,000 mg/kg SB groups compared to the control ( P < 0.05). Significantly higher levels of whole-body crude protein, ash, calcium, phosphorus, nutrition retention and relative mRNA of intestinal TOR were observed in 1,000 mg/kg SB group ( P < 0.05). Whole-body lipid content and hepatopancreas LPL mRNA expression in 2,000 mg/kg SB group were significantly higher than the control ( P < 0.05). Relative mRNA levels of intestinal LPL and hepatopancreas TOR were significantly higher in the 500 mg/kg SB group compared to those in other groups ( P < 0.05). The increased growth performance, digestive enzymes and nutrient retention in fish fed the diets supplemented with SB at 500 and 1,000 mg/kg suggests that SB can be a desirable growth promoter as an antibiotic alternative in diets.