METABOLOMIC AND NUTRITIONAL RESPONSES IN YELLOW PERCH Perca flavescens FINGERLINGS FED DIFFERENT DIETARY STARCHES

Yellow perch (Perca flavescens) are an important food fish and ecological species in the Midwestern United States. Fatty liver and over accumulation of visceral lipid is commonly observed in yellow perch fed commercial feeds. The objectives of this study were to determine whether accumulated liver and visceral lipid in yellow perch can be alleviated by feeding an appropriate starch source and investigate the underlying mechanism in relation to dietary carbohydrate utilization in yellow perch.

Yellow perch (initial body weight, 13.1±1.6 g) were fed a control diet (no added starch; protein, 54%; lipid, 12.5%) and three diets with corn, potato or wheat starch (200 g/kg diet; 41%; lipid, 12.4%)) to replace an equal proportion of fishmeal in the control diet.  The feeding trial was conducted in an indoor system run with flow-through water at 22 °C.  At the end of 8-week feeding, all fish fed the test diets had similar growth rates and feed conversion ratio (p > 0.05). However, the wheat starch diet resulted in significantly enlarged livers and increased accumulation of lipid in the liver, viscera, and whole body (p < 0.05). Wheat starch diet also caused significantly higher levels of fasting glucose, aspartate aminotransferase and alkaline phosphatase activities in serum than the control diet. Liver cell diameters were larger, and Kupffer cell numbers were lower in the fish fed the wheat starch diet than those fed the control diet. Potato or corn starch had less impact on fish health.

Results based on metabolomic pathway analysis showed that the branched-chain amino acids as well as proline were lower in fish fed the starch-based diets when compared to the control diet.  Principle component analysis (PCA) score plots for liver extracts showed a clear separation between the fish fed the control diet and wheat starch diet based on liver metabolomes. The levels of alanine, glutamate and glutamine were higher in yellow perch fed the wheat starch diet compared with fish fed the control diet. The wheat starch diet also significantly affected purine and glutathione metabolism in yellow perch. The current study suggested that potato or corn starch had less impact on fish health and metabolic profile and is considered to be an appropriate carbohydrate sources for yellow perch under the current testing conditions.