Evaluation of growth performance and metabolic efficiency in Labeo rohita fed a sorghum-based diet supplemented with chromium chloride hexahydrate

The increasing costs of fish feed in the aquafeed industry have highlighted the need to explore non-conventional carbohydrate sources that can sustain fish growth and health. Integrating carbohydrates with chromium compounds has emerged as a viable strategy to enhance energy efficiency and improve the overall health of fish. To explore this, sorghum was utilized as the carbohydrate source in a 90-day feeding trial designed to evaluate the impact of Cr₂Cl₃•6H₂O supplementation on the growth performance and metabolic parameters of Labeo rohita. Four experimental diets were formulated, containing 0, 0.3, 0.5, and 0.7 mg of Cr₂Cl₃•6H₂O per kilogram, labeled as D1, D2, D3, and D4, respectively. Different growth parameters, such as percentage weight gain, specific growth rate (SGR), protein efficiency ratio (PER), and body length, exhibited optimum values, while feed conversion ratio (FCR) recorded the lowest value at 0.3 mg Cr₂Cl₃•6H₂O/kg diet. Moreover, a significant quadratic relationship (p < 0.001) between Cr₂Cl₃•6H₂O supplementation and SGR identified an optimal inclusion level of 0.345 mg/kg in feed formulation. The digestive enzymes amylase and protease activity increased in D2 treatment. The liver cholesterol and triglyceride levels decreased at 0.3 mg Cr₂Cl₃•6H₂O/kg, while the highest level of high-density lipoprotein (HDL) and the lowest level of low-density lipoprotein (LDL) were observed at 0.5 mg Cr₂Cl₃•6H₂O/kg in the diet. The glycogen contents increased; urea and creatine contents decreased at 0.3 mg Cr₂Cl₃•6H₂O/kg. Insulin activity increased by addition of Cr. The enzymes PEP kinase and FDPase activity increased up to 0.5 mg while G6PDH at 0.3 mg Cr₂Cl₃•6H₂O/kg; then, activity of these enzymes decreased by further addition of Cr. The minimum value of SOD was at 0.3 mg Cr₂Cl₃•6H₂O/kg, ALT and AST values at 0.5 mg Cr₂Cl₃•6H₂O/kg diet while gill ATPase activity slightly increased by increasing the Cr in fish feed. The results indicated that the optimal inclusion level of Cr₂Cl₃•6H₂O in a sorghum-based diet was 0.3–0.5 mg/kg, which supported superior growth performance, enhanced digestibility, and improved metabolic efficiency in fish.