Improvement of dietary value of live foods for fish larvae by feeding them on .OMEGA.3 highly unsaturated fatty acids and fat-soluble vitamins.

Abstract

Experiments were conducted in order to improve the dietary value of live foods, such as rotifers, Artemia nauplii and Moina, by allowing them to feed on ω3 HUFA and fat-soluble vitamins by the dirct method. In this method lipids containing ω3 HUFA and fat-soluble vitamins were given, together with baker's yeast, directly to living feeds in the form of a homogenate of lipid with a small amount of raw egg yolk and water, resulting in a stable emulsion. In experiments conducted on a small scale rotifers were found to take up lipids very easily from the emulsion. The concentration of ω3 HUFA in rotifers was proportional to the content of ω3 HUFA in the emulsion, and reached a maximum after between 6 and 12h of feeding. The same kinds of results were obtained with rotifers in the experiment conducted on a large scale comparable to that required for the practical seed production of fish. Results similar to those in rotifers were obtained in both Artemia nauplii and Moina, although the concentration of ω3 HUFA in the nauplii fatty acids was far less than that in rotifers and Moina. Supplemental vitamins A and E, added to lipid. were both found to be incorporated by rotifers together with the ω3 HUFA. On the other hand, there was no marked difference in the concentration of ω3 HUFA in living feeds due to the difference of emulsifier among soybean lecithin, casein-Na, or raw egg yolk. Thus, the direct method has been shown to be effective for improving the dietary value of live foods in the same manner as the indirect method.