Dehulled solvent-extracted soybean meal as a protein source in diets for Atlantic salmon, Salmo salar L.

Diets, containing dehulled, solvent-extracted soybean meal in amounts corresponding to 0. 20 and 40% soybean protein of total protein, were fed for 10 months to duplicate groups of Atlantic salmon, Salmo salar L., weighing about 900 g, held in sea water. Fish fed the diet containing 20% soybean protein grew as well as fish fed the diet with high-quality fish meal as the sole protein source, whilst the fish fed the diet containing 40% soybean protein grew significantly less. No significant differences were found for dressing percentage, condition factor or relative liver weight between the dietary treatments. Fish fed the control or the 20% soybean meal (SBM) diets were not significantly different in body fat content, whilst this was significantly lower in the fish fed the 40% SBM diet. There were no significant differences between the dietary treatments in body protein content. Inclusion of SBM seemed to affect neither carcass calcium, carcass zinc, nor plasma calcium, magnesium or potassium. The plasma zinc content increased and plasma iron decreased by inclusion of SBM in the diets, probably reflecting dietary contents of zinc and iron. Liver iron was not affected. Plasma phosphate was significantly decreased by inclusion of SBM in the diet, whilst plasma glucose, total protein and haemoglobin were not affected. For plasma free amino acids, the only significant differences were a decrease in taurine with increasing SBM inclusion and methionine was significantly higher for the SBM groups than for the control groups.