Digestibility of fat and fatty acids in rainbow trout and mink

Abstract

The digestibility of different fats in rainbow trout and mink showed somewhat higher values in mink than in fish. Digestibility coefficients in fish did not exhibit distinct differences between two water temperatures (3 and 11°C). Rainbow trout and mink responded very similarly to digestibility differences between dietary fats and fatty acids. Both species revealed decreasing digestibility of total lipids and fatty acids with increasing melting point. Thus soybean oil, cod liver oil and capelin oil were efficiently digested, while hydrogenation of capelin oil resulted in decreased digestibility. Mild hydrogenation to 21°C melting point had a slight effect. The digestibility of saturated and unsaturated fatty acids were similarly influenced by hydrogenation. The digestibility of individual fatty acids decreased with increasing chain length up to C 18. A further increase in chain length up to C 22 caused increased digestibility. Unsaturated acids showed higher digestibility than their saturated counterparts.