Alcohol soluble components of soybeans seem to reduce fat digestibility in fish-meal-based diets for Atlantic salmon, Salmo salar L.

A commercially available soybean molasses (alcohol extract from soybean meal) was included at levels of 0. 5,10,15 and 20% in a fish meal based diet for Atlantic salmon, Salmo salar L., weighing about 75 g. These inclusion levels supplied dietary alcohol soluble components corresponding to levels that would have been obtained if a standard soybean meal was included at levels up to about 70%. The fish were reared in fresh water at 9^oC and with a minimum of 7 ppm O₂ at outlet, and fed the experimental diets for 14 days before the faeces were stripped. Digestibility coefficients were determined using chromic oxide as an indigestible indicator. The digestibility of fat, and particularly the long-chained, saturated-and monounsaturated fatty acids, were significantly reduced by increasing the inclusion level of soybean molasses, whereas digestibility of dry matter, protein (%N x 6.25) and polyunsaturated fatty acids were not affected significantly. The present results show that alcohol-soluble components of soybeans may be responsible for a significant part of the negative effects of standard soybean meal in diets for Atlantic salmon.