J. Rainuzzo, I. Overrein, K. Hamre
Fish oils and emulsions rich in essential fatty acids are often used to enrich the live feed for marine fish larvae, in order to fulfil the nutritional requirements of the larvae. Four commercial oils and one commercial emulsion were partially and fully oxidised by using an oxidative stability instrument. The oils were added emulsifiers after the oxidation and were used both in oxidised and unoxidised condition in production of live feed. Rotifers, which received the emulsions, showed a significant decrease in the quantitative content of essential fatty acids. The relative levels (percentage of total fatty acids) of these fatty acids were however about the same in rotifers receiving oxidised and unoxidised oils. A loss of amino acids was found after the rotifers were enriched with oxidised emulsions, but this was not the case when the oxidised liver oil-based emulsion was used. The loss of the essential amino acids methionine and arginine was high when the commercial emulsion was used. After 48 h of enrichment with oxidised emulsions, both growth and survival of the rotifers were satisfactory. Similar experiments were performed with Artemia. There were no differences in the amino acid content and composition between the Artemia fed oxidised and unoxidised emulsions. The content of docosahexaenoic acid (22:6n-3) in Artemia given oxidised emulsions decreased in both absolute and relative values. The total lipid content however did not change significantly. Feeding rotifers and Artemia with oxidised emulsions resulted in different effects. In rotifers, both the lipid and protein quality changed significantly. When Artemia received the same treatment only the lipid quality was negatively affected.
(SINTEF Center of Aquaculture, N-7034 Trondheim, Norway)