Notes on the Use of Supplements for Fresh Meat in the Propagation of Brook, Rainbow and Brown Trout in Michigan

Brook (Salvelinus f. fontinalis), rainbow (Salmo gairdnerii irideus), and brown trout (Salmo trutta) fingerlings were fed diets in which fresh meats were supplemented with dry animal and plant meals. Ten diets were employed including one of pure sheep liver for comparison. Trout fed diets that contained dry meals were reared at a lower cost per pound of trout (except in one case among the rainbow trout) than the controls. The mortality among the trout that received sheep liver plus dry meals in the diet was generally about as low (in some instances lower) as that of the controls, whereas the loss among those trout that received trimmed pork “melts” (spleen from which fat has been trimmed) in the diet could in no case be compared favorably with the losses among the other trout. An epidemic of ulcer disease was most severe among the fish which were fed pork “melts.” Pure sheep liver yielded the greatest increase in weight among brook and rainbow trout. Among the brown trout two of the diets that contained dry meals produced better growth than did pure sheep liver. The best conversion of food (“as purchased” basis) into body tissue was obtained from some of the diets containing dry meals.