Dietary Incorporation of Ractopamine Hydrochloride Improves Body Composition and Metabolic Enzyme Activity in Calbasu, Labeo calbasu Fingerlings, despite High- and Low-Protein-Supplemented Diet

Abstract

A 60-day feeding trial was conducted to examine the effect and interaction of dietary ractopamine hydrochloride (Rac) supplementation in diets with varied levels of protein and lipid for L. calbasu fingerlings. To attain this, the fish body compositions, digestive and metabolic enzyme activity were assessed. In total, nine diets were fed in triplicates to four hundred and five healthy Calbasu, Labeo calbasu fingerlings, based on ractopamine supplementation, viz., control (0 mg/kg), T1 (10 mg/kg), and T2 (20 mg/kg). The diets were further assigned in different levels of protein and lipid, viz., 35% protein and 6% lipid, 30% protein and 9% lipid, and 25% protein and 12% lipid. At the end of the trial, it has been observed that the inclusion of ractopamine hydrochloride at 20 mg/kg-1 of basal diet significantly ( $p<0.05$ ) improved the protein content in fed fish compared to the control. In addition, metabolic enzyme activity for hexokinase, glucose-6-phosphate, and glucose-6-phosphate dehydrogenase along with aspartate amino transferase and alanine amino transferase activity were significantly ( $p<0.05$ ) improved with the inclusion of 20 mg/kg ractopamine hydrochloride. However, the supplementation of ractopamine hydrochloride does not improve ( $p>0.05$ ) digestive enzyme activity, viz., amylase, lipase, and protease activity in the fed fish. Conclusively, it implies that adding ractopamine hydrochloride at 20 mg/kg of basal diet (high and low protein content) enhances the whole-body protein content and improves the metabolic enzyme activity in L. calbasu fingerlings. Hence, ractopamine hydrochloride has a beneficial effect in L. calbasu fingerlings and would be a desirable feed supplement for this new species culture system.