Effects of ractopamine hydrochloride on the toxicity, growth performances, body tissue compositions, residual and pharmacokinetics in tilapia (Oreochromis mossambicus)

The aim of this study focused on the study of the effects of the ractopamine hydrochloride (RAC) on the toxicity, growth performances, body composition, residual, and pharmacokinetics in tilapia (Oreochromis mossambicus). Total 198 tilapia were randomly separated into 3 groups as high dose RAC group (oral administration with 60 ppm RAC), low dose RAC group (oral administration with 30 ppm RAC), and the control group (oral administration with methanol that volume was the same as RAC groups). Tilapia in both RAC groups were fed with RAC-contained diets for 12 weeks, continuously. The detection condition settings of high-performance liquid chromatography (HPLC) included Cosmosil 5C18-MS-II column and ultraviolet (UV) light detector as station phase. The mobile phase included acetonitrile : 7 mM ammonium acetate solution (15 : 85, pH 8) and 1.1 mL/min flow rate were established. The results showed the major peak of RAC was occurred at 194 nm wavelength. There was no significant gross and histo-pathologic lesions in the heart in both RAC groups. Both RAC groups were significantly higher on body weight (BW) gain compared with the control group. Additionally, there was the highest level of muscular protein in the high dose RAC group. Muscular lipid level was decrease following with the dietary RAC in a dose-dependent manner. After oral administration with 60 ppm BW / day of RAC, the pharmacokinetic parameters t_1/2 (half-lives), T_max (time to maximum concentration) C_max (maximum concentration), MRT (mean residence time), CL_tot (total body clearance), and AUC_0-inf (area under the concentration-time curve from 0 h to infinity) were 3.42 hr, 2.0 hr, 9.7 ppm, 4.74 hr, 964 mL hr^-1 kg^-1, and 337.8 hr × μg mL^-1, respectively. Taken all results together, we considered that tilapia were fed with diets supplemented with 30 and 60 ppm RAC had no toxicity in the heart, short withdraw time, and the positive effects on BW gain, and protein and lipid levels in muscle.