EFFECTS OF REPLACING FISH-MEAL WITH SOYBEAN-MEAL IN DIETS FOR RED DRUM SCIAENOPS-OCELLATUS AND POTENTIAL FOR PALATABILITY ENHANCEMENT

Two 8-wk feeding trials were conducted with juvenile red drum to deter mine the maximum levels of soybean meal that may replace fish meal in diets containing 38% crude protein, without reducing weight gain. In t he first experiment, fish fed diets containing up to 90% of the protei n from soybean meal gained as much weight as fish fed a diet with 100% of protein from fish meal, but fish fed the diet with 100% of its pro tein from soybean meal gained significantly (P < 0.05) less. Supplemen tation of glycine and fish solubles individually at 2% (as-fed basis) in diets containing 90% of their protein from soybean meal tended to i ncrease weight gain of fish compared to those fed a similar diet witho ut supplementation. Similar results were obtained in the second experi ment, as fish fed diets containing 90% of their protein from soybean m eal gained as much weight as fish fed a diet with 100% of its protein from fish meal. Fish fed diets with 95% and 100% of their protein from soybean meal gained significantly less weight than those fed the diet with all of its protein from fish meal. Supplementation of glycine at 2% in the diet containing 95% of its protein from soybean meal signif icantly improved weight gain of fish relative to those fed a similar u nsupplemented diet. Supplementation of fish solubles at 5% of diet on a dry-matter basis provided a nonsignificant increase in weight gain c ompared to that of fish fed a similar unsupplemented diet. In both exp eriments there was greater observed consumption of the soybean-meal-ba sed diets than diets with all of their protein from fish meal. A minim um of 10% of protein from fish meal appears necessary in practical die ts containing most of their protein from soybean meal to prevent impai red growth and feed efficiency of red drum.