The growth and well-being of carnivorous fish, such as largemouth bass (Micropterus salmoides), can be compromised by excessive dietary starch but may depend on the starch type and degree of gelatinization.
In a 2 × 2 factorial design, an international team of researchers tested diets containing 20% raw corn starch (RCS), raw sweet potato flour (RSP), pregelatinized corn starch (PGCS) or pregelatinized sweet potato flour (PGSP) on largemouth bass. Growth, muscle biochemical composition, liver/intestinal histopathology, and expression of genes responsible for the growth and fatty acid metabolism were analyzed.
Some indicators of pellet quality were also measured showing that pregelatinized starches significantly improved water stability, water absorption index, and water solubility index while significantly reducing bulk density. Gelatinization significantly improved weight gain and FCR (1073% and 0.84, respectively) over their raw starch forms (892% and 1.02, respectively).
Neither starch type or gelatinization had any significant effect on the muscle proximate or mineral composition, but MUFA was significantly in the RCS treatment, which corresponded with significantly lower hepatic expression of fatty acid synthase.
Gelatinization significantly upregulated lowest 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.
Researchers concluded 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.
Check out the study here.