Ractopamine supplementation in diets for Nile tilapia at grow-out phase: effect on body composition and fatty acid profile

Abstract Ractopamine is a drug used as an additive in animal production to improve growth, body composition and production efficiency, although its use in fish is still poorly known. This study aimed to evaluate ractopamine hydrochloride (RAC) effects at increasing levels (0, 10, 20 and 40 mg kg− 1) in Nile tilapia (Oreochromis niloticus) diets during 40 days by considering productive performance, body composition and muscle fiber morphometry. One hundred and twelve fish (mean initial weight 518.63 ± 5.49 g) were housed in 16 circular tanks (450 L), following a completed randomized design with four treatments and four replicates. Body composition was significantly affected (P < 0.05) and the amount of lipids in fish fillets dropped 26,7% (20 mg.kg− 1 RAC) and 26,1% (40 mg kg− 1 RAC), as well as the amount of unsaturated fatty acids C14:0 and C18:0 in fish fillets (P < 0.05) by treatment with 10 mg kg− 1 of RAC. RAC did not affect any productive performance parameters evaluated, as well for muscle fiber morphometry. Taken together, our results demonstrate that fish fed 20 mg kg− 1 RAC for 40 days changes Nile tilapia fillet chemical composition, decreasing lipid levels and altering the fatty acid profile, as well as increasing protein levels.