Untersuchungen über die Fettverwertung der Regenbogenforelle (Salmo gairdnerii,R.) VI: Vergleichender Einsatz von 18 unterschiedlichen Futterfetten in einer gereinigten Diät

Investigations about Fat Utilization of the Rainbow Trout (Salmo gairdnerii, R.) VI: Comparative Use of 18 Different Feeding Fats in a Purified Diet In the submitted work the usability of different feeding fats as source of energy in rations for rainbow trouts is reported. In comparison to 10% of sunflower oil in a standard diet the same amount of examined fats (maize germ oil, rice oil, lard, Novitol-30) with a share of less than 3% of essential linolenic acid (18:3, n-3) produced a just so good utilization. Only olive oil with an unbalanced high content of oleic acid decreased significantly. If a share of 6–7% in 18:3, n-3, fatty acids was contained in the feeding fat (rape seed oil poor in erucic acid and rich in erucic acid, raw and refined soya bean oil, refined soya fatty acids) the utilization increased significantly. The best result was achieved by addition of refined soya fatty acids with 15% 18:3, n-3, or red perch oil with a share of 17% 20:5, n-3 and 22:6, n-3. If beef tallow and especially micronized hardened fatty acids were used whose melting point was far beyond 40°C, a significant decrease in utilization was noticed. These fats proved to be less suitable as source of energy in rations for rainbow trouts. The same good characteristics of utilizations as with soya bean oil and rape seed oil were found in case of use of mixed animal fats, though no essential fatty acids were contained. An explanation could not be found. Linseed oil came off badly, though a surplus of essential fatty acids 18:3, n-3 was contained. The high rate of oxidations of the three fold unsaturated linolenic acid and as result a lacking absorption might be the cause.