Replacement of fish meal with rapeseed protein concentrate in diets fed to wels catfish (Silurus glanis L.)

The potential of rapeseed protein concentrate as fish meal alternative in diets for wels catfish (initial average weight 86.5 +/- 1.9 g) was evaluated. Sixteen fish were stocked into each of 12 experimental tanks being part of a freshwater recirculation system. Fish were organized in triplicate groups and received isonitrogenous (603 +/- 3 g CP kg(-1)) and isocaloric (23.0 +/- 0.3 kJ g(-1)) experimental diets with 0%, 25%, 50% and 75% of fish meal replaced with rapeseed protein concentrate (710 g CP kg(-1)). At the end of the 63-day feeding period, weight gain, standard growth rate, feed intake, feed conversion ratio and protein efficiency showed no significant difference between control group and fish fed on diets with 25% reduced fish meal content by inclusion of rapeseed protein concentrate. Higher dietary fish meal replacement negatively affected diet quality and palatability resulting in reduced feed intake, feed efficiencies and fish performance. However, blood serum values of triglycerides, glucose and protein were not significantly different between treatment groups, still indicating a favourable nutrient supply from all experimental diets.