EFFECTS OF DIETARY-PROTEIN - ENERGY RATIO ON WEIGHT-GAIN, BODY-COMPOSITION, SERUM GLUCOSE AND TRIGLYCERIDE LEVELS, AND LIVER-FUNCTION OF STRIPED BASS

A 12 week feeding experiment was conducted with juvenile, full sibling striped bass (Morone saxatilis) to evaluate three practical diets wit h 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, g rowth in diet 1 and 2 was significantly less than in diet 3. Proximate composition of whole fish indicated that striped bass fed Diet 1, wit h the lowest level Of metabolizable energy but the lowest protein:ener gy ratio, had significantly higher lipid content compared to the remai ning diets. Conversely, diet 3, with the highest level of metabolizabl e 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-expe rimental levels, but were lowest in diet 3, Serum glucose levels dropp ed from pre-experimental levels in all treatments except diet 1. A lin ear increase in both lipids and carbohydrates stored in the cytoplasm of the liver hepatocytes was observed with increasing metabolizable en ergy content of the diets. Hepatocellular swelling was observed in fis h fed all three diets, However, the two lower protein:energy ratio die ts caused significantly greater swelling of hepatocytes than did the h ighest protein:energy ratio diet. These data indicate that similar pra ctical diets with less than 34 g protein/MJ may be inappropriate for j uvenile striped bass.