Residue Depletion of Ractopamine and Its Metabolites in Swine Tissues, Urine, and Serum

Abstract

Ractopamine hydrochloride is a beta-adrenergic leanness-enhancing agent approved for use in swine in the United States. Depletion of ractopamine and its metabolites from animal tissues, urine, and serum is of interest for the detection of illegal use. The objectives of this study were to measure the residues of ractopamine in swine incurred samples after treatment with dietary ractopamine for 28 consecutive days. An efficient and sensitive analytical method was developed for the detection of parent ractopamine and its metabolites in swine tissues, urine, and serum by HPLC-FLD. After extraction, enzymatic digestion, and solid-phase cleanup of the samples, ractopamine residues were determined by liquid chromatography (LC) with fluorescence detector. The limits of detection (LOD) for tissues, urine, and serum were 1 ng g(-1), 0.5 ng mL(-1), and 0.5 ng mL(-1), respectively. Recoveries ranged from 70.5 to 94.5% for samples fortified at 1-50 ng g(-1) or ng mL(-1). Sixty pigs were fed twice daily for 28 consecutive days with feeds containing 18 mg kg(-1) ractopamine HCl. The residue concentrations in urine, liver, and kidney were 650.06 ng mL(-1), 46.09 ng g(-1), and 169.27 ng g(-1), respectively, compared with those in muscle, fat, and serum (4.94 ng g(-1), 3.28 ng g(-1), and 7.48 ng mL(-1), respectively) at the feeding period of 7 days. The residue concentrations at withdrawal period of 0 days in all edible tissues were lower than tolerance values established by the FDA and MRL values listed by the JECFA. These data support the withdrawal time of 0 days established by the FDA for ractopamine used as feed additive in swine.

Determination of Ractopamine Residues in Pigs by Ultra Performance Liquid Chromatography Tandem Mass Spectrometry

“…Literature data indicate that swine eliminate nearly 85% of the ractopamine administered during the first day, resulting in relatively low tissue residues (Dalidowicz et al, 1992). In comparison with some literature data (Qiang et al, 2007;Smith & Shelver, 2002), low concentrations of ractopamine urinary residues determined in our study could be explained by low exposure of animals to ractopamine. Fig.…”

“…The concentration of ractopamine in urine samples processed with enzyme hydrolysis was almost 10-fold that recorded in urine samples analyzed without enzyme hydrolysis. Deconjugation step confirmed ractopamine to be excreted mainly in the form of glucuronide metabolites, as reported previously (Qiang et al, 2007;Shelver & Smith, 2003). Therefore, further analyses (hair) were performed exclusively with sample hydrolysis and values obtained with sample enzyme hydrolysis were used on interpretation of the urine ractopamine concentrations.…”

“…Control and monitoring programs mandated by government have also necessitated implementation of assays for determination of ractopamine accumulation and excretion from tissues and body fluids in farm animals. Studies of ractopamine residue detection after different treatment schedules in different animal species have been reported by several authors (Elliot et al, 1998;Qiang et al, 2007;Smith & Shelver, 2002;Thompson et al, 2008). Published studies report on tissue residues of ractopamine and its urinary excretion (Antignac et al, 2002;Blanca et al, 2005;Dickson et al, 2005;Moragues & Igualada, 2009;Nielen et al, 2008;Thompson et al, 2008;Van Hoof et al, 2005) and ractopamine residues in hair (Nielen et al, 2008).…”

“…Therefore, further analyses (hair) were performed exclusively with sample hydrolysis and values obtained with sample enzyme hydrolysis were used on interpretation of the urine ractopamine concentrations. Earlier investigations performed in pigs with the use of a higher ractopamine anabolic dose (18 mg ractopamine hydrochloride/kg of feed) showed significantly higher concentrations of ractopamine in urine, with mostly twofold concentrations determined with sample enzyme hydrolysis (Qiang et al, 2007). Studies carried out in cattle and sheep report on detectable ractopamine residues in urine 5 to 7 days after the last exposure to dietary ractopamine, pointing that hydrolysis of ractopamine metabolites may extend the period in which it is detected in cattle (Smith & Shelver, 2002).…”

Effects of ractopamine plus amino acids on growth performance, carcass characteristics, meat quality, and ractopamine residues of finishing pigs

“…Most of the studies available on RAC use growth performance traits (Aalhus et al, 1990;Barker et al, 2005;Ross et al, 2011) or carcass measurements, meat quality and sensory attributes (Fernández-Dueñas, 2008;Kutzler et al, 2011), but few studies have reported tissue residue concentrations (i.e., muscle and liver). Some studies have focused on comparing techniques to quantify residues (Shishani et al, 2003;Qiang et al, 2007;Sakai et al, 2007), but to our knowledge, there are no complete studies using RAC that reported live animal performance, carcass and meat characteristics, and residue concentrations in target tissues. Thus, the objective of this study was to investigate the effects of the addition of RAC plus amino acids on growth performance, carcass characteristics, cuts yield, meat quality, sensory attributes and residues in liver and muscle of finishing pigs.…”