Pregelatinized starch improves growth and mitigates adverse liver/intestinal histomorphology in largemouth bass, Micropterus salmoides, juveniles

The growth and well-being of carnivorous fish, such as largemouth bass Micropterus salmoides, can be compromised by excessive dietary starch but this may depend on starch type and degree of gelatinization. In a 2 × 2 factorial design, largemouth bass were fed diets containing 20 % raw corn starch (RCS), raw sweetpotato flour (RSP), pregelatinized corn starch (PGCS) or pregelatinized sweetpotato flour (PGSP) and their growth, muscle biochemical composition, liver/intestinal histopathology, and expression of genes responsible for growth and fatty acid metabolism were analyzed. Some indicators of pellet quality were also measured showing that pregelatinized starches significantly improved (P < 0.05) water stability, water absorption index, and water solubility index while significantly reducing bulk density. Gelatinization significantly improved (P < 0.05) weight gain and FCR (1073 % and 0.84, respectively) over their raw starch forms (892 % and 1.02, respectively), which was correlated with significantly upregulated (P < 0.05) hepatic insulin-like growth factor-1. Neither starch type or gelatinization had any significant effect on the muscle proximate or mineral composition, but MUFA was significantly (P < 0.05) in the RCS treatment, which corresponded with significantly lower hepatic expression of fatty acid synthase. Gelatinization significantly upregulated lowest (P < 0.05) hepatic expression of cholesterol 7 alpha-hydroxylase. Histopathological damage and inflammation occurred in the liver and distal intestine, respectively, of fish fed raw starch diets but not for the PG types. Results indicate that pregelatinizing both starch sources significantly improved growth and feeding efficiency in largemouth bass juveniles while causing no adverse histopathology compared to either raw starch sources.