Effect of different dietary fiber concentrates on the metabolism and indirect immune response in silver catfish

• Dietary fiber concentrates benefit fish metabolism.
• Yeast autolysate and linseed fiber increased skin mucosa production.
• Dietary fiber concentrates could act as potential prebiotic agents in fish diets.

This work aims at assessing the metabolic and immunologic indirect responses of the addition of dietary fiber as a prebiotic agent to the diets of silver catfish (Rhamdia quelen). Dietary fiber was concentrated from citrus pulp, brewery yeast biomass and linseed grains. These were prepared and included in diets, as well as a treatment control and a commercial diet containing prebiotic (Actigen®). During 50 days, 600 juveniles silver catfish were maintained in a water recirculation system and fed with experimental diets, three times a day. At the end of the test, the animals’ blood, liver, mucus and intestine were collected for determination of the metabolic and immunologic parameters. The experimental design was completely randomized, with five treatments and four replications; data were subjected to the analysis of variance, and the means were compared by the Tukey’s test (P < 0.05). Fiber concentrates the differences in composition and physical-chemical properties, which resulted in differences in blood parameters, intestinal goblet cell counts, hepatic metabolic intermediates and mucoprotein production by fish. Yeast autolysate and linseed fiber provide prebiotic effects when added to silver catfish diets, bringing benefits to the metabolism and animal’s immune system.