The effects of dietary supplementation with mannanoligosaccharide, fructooligosaccharide or galactooligosaccharide on the growth and feed utilization of Atlantic salmon (Salmo salar)

As a potential method for improving the health and growth of Atlantic salmon, dietary supplements of the prebiotics mannanoligosaccharide (MOS), fructooligosaccharide (FOS) in the form of inulin and galactooligosaccharide (GOS) were assessed in a 4-month trial. The prebiotics were added at a level of 10 g kg− 1 to a fish meal-based control diet and each diet was fed to triplicate groups of 200 g salmon in tanks supplied with salt water. Feed intake, growth, digestibility, body composition and routine oxygen consumption of the fish were monitored, as well as the non-specific immune system.The fish were healthy and no mortality occurred. There were no treatment effects on feed intake, growth or digestibility. Feed efficiency was 5% and energy retention 6% greater in the salmon fed the FOS diet than in those fed the basal diet (nonorthogonal contrasts; P < 0.05). The fish fed the MOS diet showed 11% lower routine oxygen consumption, 5% lower protein and 3% higher energy concentration in the whole-body and 7% greater energy retention than in the fish fed the basal diet (P < 0.05). In salmon fed the GOS diet, the nitrogenous and energetic losses in the non-faecal nitrogen excretions were 11 and 7% higher, respectively, and the protein concentration in the wet body and protein retention were reduced by 6 and 9%, respectively, relative to the basal fish (P < 0.05). The contrasts showed that neutrophil oxidative radical production and serum lysozyme activity at the end of the 16-week trial were significantly lower in the fish fed the MOS diet compared with those fed the basal diet.The results of this trial indicate that at the level used, supplementation of the diet with FOS or MOS seem to be most positive for salmon production.