Dietary fiber in the nutrition of silver catfish: Prebiotic or antinutrient?

• There is limited information on the potential of prebiotic dietary fiber for fish.
• Yeastautolysate and linseed fiber acts as a growth promoter for silver catfish.
• Yeastautolysate and linseed fiber provide higher deposition of nutrients by animals.
• Inclusion of citrus pulp reduces food intake by silver catfish.

This study was conducted to evaluate the prebiotic potential of dietary fiber as a growth promoting agent in a juvenile silver catfish diet (Rhamdia quelen) regarding performance, deposition of nutrients and production of digestive enzymes. The treatments were: control diet, a diet containing commercial prebiotic Actigen®, inclusion of citrus pulp, yeast autolysate and linseed fiber. During 50 days, 600 juvenile silver catfish (3.54 ± 0.53 g) were kept in a water recirculation system and fed three times a day with the experimental diets. At the end of the experiment, the growth parameters, nutrient deposition, corporal yield, digestive index and digestive enzymes were evaluated. The experimental design was a randomized, with five treatments and four replications, the data were subjected to analysis of variance and means were compared by Tukey test (P < 0.05). Fish fed diets containing yeast autolysate and linseed fiber showed superior performance (P < 0.05) to the other treatments tested, as well as higher values of crude protein and fat deposited in the body. Animals fed diets containing citrus pulp showed lower performance and nutrient deposition. Corporal yield, digestive index and production of digestive enzymes were not affected by the tested fibers. In conclusion, the results have showed that yeast autolysate and linseed fiber provide better performance and nutrient deposition by animals, demonstrating the potential prebiotic effect of the use of these ingredients in the nutrition of juvenile silver catfish.