Accumulation of ractopamine residues in hair and ocular tissues of animals during and after treatment.

The aim of the present study was to assess the accumulation of ractopamine residues in the hair and ocular tissues of guinea pigs during repeated ractopamine administration and after treatment. The experiment was conducted in 38 guinea pigs (30 treated and eight controls). Treated animals were orally administered ractopamine hydrochloride in a dose of 3.5 mg/kg body mass per day using probes for seven consecutive days. Ractopamine concentration was determined in hair during the treatment (Days 1, 3 and 7) with ractopamine hydrochloride and in ocular tissues and hair on defined days after exposure (Days 1, 10, 20 and 30). Residues were present in hair in high concentrations as early as Day 3 (86.15 ± 87.71 ng/g) and Day 7 (85.25 ± 56.97 ng/g). After exposure, residues were found to persist, having depleted from 68.06 ± 30.54 ng/g on Day 1 to 8.01 ± 2.22 ng/g on Day 30, with a significantly higher concentration in hair in contrast to low residue levels in ocular tissues (1.20-0.34 ng/g). The results of the study pointed to high ractopamine accumulation, even in non-pigmented hair, suggesting hair to be used as a matrix in the control of ractopamine abuse in farm animals because of its many advantages over ocular tissues.