Practical Diets Formulated With Different Plant‐Based Energy Ingredients Modulate Nutrient Utilization and Gut Morphology in Tambaqui ( Colossoma macropomum )

Despite the increasing use of plant‐based energy ingredients in aquaculture, few studies have evaluated the digestibility of practical diets formulated with these ingredients in an integrated manner with the metabolic responses, intestinal health, and productive performance of fish. This limits the understanding of their nutritional effects. This study evaluated the apparent digestibility of nutrients and energy from starch‐rich practical diets and their effects on growth performance, intestinal fold histomorphometry, and metabolic and physiological profiles of tambaqui ( Colossoma macropromum ). One hundred and ninety‐two tambaqui juveniles (131.63 ± 1.94 g) were fed six experimental, pelleted diets formulated with corn (CO), cornstarch (CS), sorghum (SO), wheat bran (WB), rice bran (RB), or broken rice (BR). The apparent digestibility coefficients of dry matter (ADC DM ), organic matter (ADC OM ), ether extract (ADC EE ), crude protein (ADC CP ), gross energy (ADC GE ), and starch (ADC ST ) were analyzed. ADC DM (31.8%–71.9%), ADC OM (44.5%–76.6%), and ADC GE (48.0%–72.6%) varied among the diets but followed a similar pattern: values for the diets with CO (63.3%, 71.7%, and 72.6%, respectively), CS (71.9%, 76.6%, and 79.2%, respectively), and broken bran (65.6%, 72.4%, and 72.5%, respectively) were higher than those for the diets with WB (41.0%, 52.2%, and 53.8%, respectively) and RB (31.8%, 44.5%, and 48.0%, respectively). ADC CP and ADC EE were > 70% in all diets, except that with WB. ADC ST was > 90% for all diets. Plasma glucose and serum cholesterol concentrations were similar across treatments. Diets including WB and RB resulted in less‐developed intestinal folds, which led to lower digestibility and, consequently, reduced growth. In contrast, diets formulated with SO, BR, or CS proved to be viable alternatives to the CO‐based diet, promoting comparable nutrient and energy digestibility. Tambaqui exhibited metabolic adaptation to the physicochemical properties of these formulations, maintaining productive performance. However, the inclusion of WB and RB should be limited because of the high fiber content, which can compromise intestinal health and nutrient utilization efficiency.