Three isocaloric diets were prepared. Diet 1 (Control) contained 22% herring oil. In diets 2 and 3, a third and a half of the herring oil was replaced, respectively, by an animal fat (lard) which contained a high percentage of saturated fatty acids. Each diet was fed to duplicate groups of rainbow trout for 14 wk. The results of the feeding trial indicated that the concentration of the saturated fatty acids in trout body lipid did not increase despite the high concentration of these fatty acids in Diets 2 and 3. Fish growth, feed efficiency, mortality and the level of fatty acids deposited in fish body lipid and phospholipids are discussed.
Four samples of corn were compared with respect to their hepatocarcinogenicity in rainbow trout. One corn sample was found by chemical analysis to contain no detectable aflatoxin. A second sample was contaminated with aflatoxins at a level of 180 ,ug/kg. Each of the above-mentioned samples was divided, and onehalf of each was ammoniated. These four samples were added to a semipurified basal diet and fed to a sensitive strain of rainbow trout. It was found that ammoniation inactivated the aflatoxins and reduced the carcinogenicity of the contaminated corn to a level that was not significantly different from that with the basal control diet. It was also found that the ammoniation process did not reduce the nutritive value of the corn.
We investigated the growth of rainbow trout (Salmo gairdneri) fed diets containing an animal fat (lard) as a source of energy. Nine diets, identical in gross energy, but containing three levels of protein, were each fed to duplicate groups of fish for 14 weeks. The control diets contained 22% herring oil; in the test diets, 33 and 50% of the dietary herring oil was replaced by lard. The final fish weight, feed consumption, feed efficiency, and fish liver size were about the same in the groups of fish receiving control and test diets containing the same protein level.
The natural food of salmon and trout is composed
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