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A 12 week feeding experiment was conducted with juvenile, full sibling striped bass (Morone saxatilis) to evaluate three practical diets with protein:energy ratios of 26.9 (diet 1), 31.1 (diet 2), 35.7 (diet 3) g protein/MJ energy. Survival was high in all three diets, however, growth in diet 1 and 2 was significantly less than in diet 3. Proximate composition of whole fish indicated that striped bass fed Diet 1, with the lowest level of metabolizable energy but the lowest protein:energy ratio, had significantly higher lipid content compared to the remaining diets. Conversely, diet 3, with the highest level of metabolizable energy and the highest protein:energy ratio, was the only diet with an increased whole body protein content. Serum levels of triglycerides increased significantly in all treatments when compared with pre-experimental levels, but were lowest in diet 3. Serum glucose levels dropped from pre-experimental levels in all treatments except diet 1. A linear increase in both lipids and carbohydrates stored in the cytoplasm of the liver hepatocytes was observed with increasing metabolizable energy content of the diets. Hepatocellular swelling was observed in fish fed all three diets. However, the two lower protein:energy ratio diets caused significantly greater swelling of hepatocytes than did the highest protein:energy ratio diet. These data indicate that similar practical diets with less than 34 g protein/MJ may be inappropriate for juvenile striped bass.

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Rainbow trout were grown for 16 weeks at 12°C in flow-through outdoor tanks with demand feeders. Four commercial diets were tested: Zeigler Hi-Fat Trout Grower (38% protein, 12% fat), Balshi Trout Grower (38% protein, 10% fat), Brown High Fat Trout Grower (38% protein, 12% fat), and Zeigler High Performance Trout Grower (45% protein, 12% fat). Survival was high (>98%) on all diets. The Zeigler Hi-Fat diet gave significantly greater length gain than the Zeigler High Performance diet, but otherwise these two diets yielded similar results. The Balshi diet performed similarly to the Zeigler Hi-Fat diet, but feed conversions and phosphorus losses to the environment were significantly greater. The Brown diet was significantly inferior to the other diets in terms of weight and length gains, feed conversions, fish-fillet protein content, and phosphorus losses. Nephrocalcinosis was observed only in fish fed the Balshi and Brown diets, but the incidence was not statistically significant.