EFFECT OF DIETARY OIL ON THE FATTY ACID COMPOSITION OF RAINBOW TROUT OIL

Recently much attention has been given to the enrichment of diet for fish by the ad-dition of oil. Among the serious problems concerning it are the effects of dietary oil on the quality and quantity of the raised fish. The present paper is concerned with the effects of dietary oil on the fatty acid composition of rainbow trout (Salmo gairdnerii irideus) which were fed on the various oil sources, gas-liquid chromatography being carried out for this purpose. In order to elucidate the change of fatty acid composition with the growth of the fish, the fish fed on a standard diet containing a typical marine oil (Table 1) were divided into three groups according to their body weight, namely small, medium and large one (Table 2). Data illustrated in Table 3 and Figs. 1 and 2 have shown that the fatty acid composition of these three groups were influenced by the dietary oil, especially in that of the small one, while polyunsaturated fatty acids were reduced gradually with the growth of the fish. Four groups of the fish (body weight ca. 90g) were fed for 103 days on a standard diet and whale oil-, Alaska pollack oil- and soy bean oil-containing diet (Tables 4 and 5). As a result, fatty acids were apparently neither synthesized nor converted in those fish fed on much amount of the latter three oils, and the nature of oil in each group was influenced by the dietary oil. Moreover it is interesting that when fed on soy bean oil, arachidonic acid, eico-sapentaenoic acid and docosahexaenoic acid were not detected in the group (Table 6 and Figs. 3 and 4).