Residue study of nitroimidazoles depletion in chicken feathers in comparison with some other selected matrixes

ABSTRACT

This paper presents the results from a residue study conducted on a statistically representative number of chicken broilers that were individually orally treated with the selected nitroimidazoles (metronidazole, ornidazole and ipronidazole) in an appropriate amount close to the theoretical therapeutic dose. A mutual persistence comparison of the monitored analytes in feathers, serum, muscle and shanks was performed and attention was also paid to selected metabolites (hydroxymetronidazole and hydroxyipronidazole). An analytical LC/MS/MS method using SupelMIP SPE nitroimidazoles cartridges was developed for the determination of nitroimidazoles residues in poultry feathers, serum, muscle and shanks and the method was validated according to Commission Decision 2002/657/EC. High concentrations of nitroimidazoles residues in feathers were observed 19 days after the broilers’ treatment unlike the muscle and serum samples, where nitroimidazoles depletion was significantly faster (residue concentrations were below detection limits in 5 days in muscle and in 12 days in serum). Shanks (chicken claws) also proved to be a very useful matrix for the detection of nitroimidazoles drugs misuse due to the longer persistence of these drugs residues and their metabolites in this matrix (determinable concentrations were observed 19 days after the broilers’ last treatment). Feathers and shanks appear to be suitable matrixes for the screening of various nitroimidazoles in poultry because long-term persistence of residues enables reliable detection of the illegal use of nitroimidazoles compounds in official checks.     

Distribution and residue depletion of oxytetracycline in giant freshwater prawn (Macrobrachium rosenbergii)

Distribution and residue depletion patterns of oxytetracycline were examined in giant freshwater prawns, Macrobrachium rosenbergii, after medicated-feed treatment at the feeding level of 4 g/kg of feed for 5 consecutive days. The concentration of oxytetracycline in prawn muscle tissues was measured using high-performance liquid chromatography equipped with a fluorescence detector. The limit of detection was 0.1 microg/g. In the medicated-feed-treated group, oxytetracycline was detectable 8 days posttreatment at the feeding level of 4 g/kg of feed for 5 consecutive days. The depletion half-life and mean residence time of oxytetracycline were 30.96 and 100.3 h, respectively. The dose of 4 g/kg of feed for 5 consecutive days can be recommended for therapeutic dosage regimen in giant freshwater prawn aquaculture. The minimal withdrawal period of M. rosenbergii muscle tissue should be 8 days postcessation of medicated feed.     

Fate of eprinomectin in goat milk and cheeses with different ripening times following pour-on administration

The distribution of eprinomectin in goat milk and cheeses (cacioricotta, caciotta, caprilisco) with different ripening times following a pour-on administration at a single dose rate (500 microg/kg of body weight) and a double dose rate (1,000 microg/kg of body weight) to goats with naturally occurring infections of gastrointestinal nematodes was studied. Milk residues of eprinomectin reached a maximum of 0.55+/-0.18 microg/kg and 1.70+/-0.31 microg/kg at the single and double doses, respectively. The drug concentrations decreased progressively until the fifth day after treatment, when they were less than the detection limit at both dose rates. The eprinomectin levels measured in all cheese types (both treatments) were higher than those recovered in milk at all the sampling times. In caciotta cheeses, the eprinomectin residues levels were constantly higher than other cheeses. With the exception of cheeses made with milk the first day after treatment, eprinomectin concentrations were nearly constant up to the fourth day then decreased by the fifth and sixth days after treatment. In all cases, at both the single and double dosages, the maximum level of eprinomectin residues in goat milk and cheeses remained below the maximum residual level of 20 microg/liter permitted for lactating cattle.     

恩诺沙星、氟苯尼考和泰万菌素在鸡蛋中残留消除规律研究

目的 评估恩诺沙星、氟苯尼考和泰万菌素在鸡蛋中的残留消除规律。方法 将80羽高产海兰褐蛋鸡随机等分成4组, 对照组饲喂基础日粮, 恩诺沙星组、氟苯尼考组和泰万菌素组分别经混饲给予相应药物, 每日1次, 连续给药5 d, 停药19 d, 检测各枚鸡蛋中相应药物及其主要代谢产物的残留量。结果 恩诺沙星及其主要代谢产物环丙沙星与氟苯尼考及其主要代谢产物氟苯尼考胺可迅速残留于鸡蛋中, 残留物分别以恩诺沙星原型和氟苯尼考原型为主, 且其残留蓄积期都超过19 d。泰万菌素及其主要代谢产物3-乙酰胺基泰万菌素在鸡蛋中的残留总量低于最大允许残留限量, 且平均残留蓄积期为7 d, 3-乙酰胺基泰万菌素占总残留量的50%以上。结论 恩诺沙星和氟苯尼考在海兰褐品系鸡蛋中残留消除周期超过19 d, 在对后备蛋鸡、肉蛋兼用鸡给药时需严格控制用法用量。在适用情况下, 可优先选择平均残留消除周期相对较短的泰万菌素。     

氟苯尼考及其代谢物氟苯尼考胺在肉鸡中残留消除规律

目的 评估氟苯尼考及其代谢物氟苯尼考胺在不同品种肉鸡中的残留消除规律。方法 选用AA肉鸡、WOD168肉鸡、雪山鸡和狼山鸡为试验对象, 于出栏前3周开始按氟苯尼考25 mg/kg体重饮水给药, 连用5 d, 于停药后1、3、5、7、10、14 d采集肌肉、肝脏、肾脏、皮脂, 检测其中的氟苯尼考和氟苯尼考胺残留量, 并利用WT1.4软件计算休药期。结果 氟苯尼考及其代谢物氟苯尼考胺可迅速残留于肉鸡肌肉、肝脏、肾脏和皮脂中, 残留物以氟苯尼考为主。停药后第1 d残留量达到峰值, 肾脏组织中的残留量最大; 停药后第3 d, 各组织中氟苯尼考和氟苯尼考胺的残留量进入快速消除期, 均低于最大残留限量值; 停药后第14 d已基本消除完全。利用WT1.4软件计算出AA肉鸡、WOD168肉鸡、雪山鸡和狼山鸡休药期分别至少为3.22、3.85、4.49和4.32 d。结论 氟苯尼考在慢速型肉鸡体内的休药期要长于快速型肉鸡, 但都小于5 d。     

Novel approach to fast determination of multiple pesticide residues using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)

A rapid, high-throughput method employing ultra-performance liquid chromatography with tandem quadrupole mass spectrometry (UPLC-MS/MS) was developed and optimized for simultaneous quantification and confirmation of 64 pesticide residues and their toxic metabolites in fruit extracts prepared by a buffered QuEChERS procedure. The total time required for UPLC-MS/MS analysis was 8 min plus 2 min for re-equilibration to the initial UPLC conditions. Performance characteristics were determined for apple extracts spiked at 10 microg kg(-1). The repeatability of measurements expressed as relative standard deviations was in the range 1.5-13% at this level for most analytes. Thanks to very low limits of quantification (<10 microg kg(-1)for the majority of pesticides), an optimized method allows for the reliable control of not only common maximum residue limits (MRLs) set by European Union regulation for various pesticides/fruit combinations, but also of a uniform MRL of 10 microg kg(-1)endorsed for baby food.     

Novel approach to fast determination of multiple pesticide residues using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).

A rapid, high-throughput method employing ultra-performance liquid chromatography with tandem quadrupole mass spectrometry (UPLC-MS/MS) was developed and optimized for simultaneous quantification and confirmation of 64 pesticide residues and their toxic metabolites in fruit extracts prepared by a buffered QuEChERS procedure. The total time required for UPLC-MS/MS analysis was 8 min plus 2 min for re-equilibration to the initial UPLC conditions. Performance characteristics were determined for apple extracts spiked at 10 microg kg(-1). The repeatability of measurements expressed as relative standard deviations was in the range 1.5-13% at this level for most analytes. Thanks to very low limits of quantification (<10 microg kg(-1)for the majority of pesticides), an optimized method allows for the reliable control of not only common maximum residue limits (MRLs) set by European Union regulation for various pesticides/fruit combinations, but also of a uniform MRL of 10 microg kg(-1)endorsed for baby food.     

Residues of sulfadiazine and doxycycline in broiler liver and muscle tissue due to cross-contamination of feed

Veterinary drugs, such as antimicrobial compounds, are widely used in poultry and may lead to the presence of residues in matrices of animal origin, such as muscle and liver tissue. In this study, broilers received an experimental feed containing sulfadiazine or doxycycline at cross-contamination levels of 2.5, 5 and 10% of the therapeutic dose in feed. Breast and thigh muscle and liver samples were collected during treatment and depletion period and analysed via liquid chromatography-tandem mass spectrometry (LC-MS/MS). Concentrations reached a plateau phase 3-5 days after the start of experimental feeding. A rapid depletion of residues was noted after withdrawal of the experimental feed. No significant differences in measured concentrations were observed between the various muscle types. Residue concentrations for some experimental groups; the 10% group of sulfadiazine and the 5 and 10% group of doxycycline, however, exceeded their corresponding maximum residue limits (MRLs).     

Depletion of tylosin residues in feathers,muscle and liver from broiler chickens after completion of antimicrobial therapy

Tylosin is one of the most commonly used antimicrobial drugs from the macrolide family and in broiler chickens it is used specially for the treatment of infectious pathologies. The poultry industry produces several by-products, among which feathers account for up to 7% of a chicken’s live weight, thus they amount to a substantial mass across the whole industry. Feathers have been repurposed as an animal feed ingredient by making them feather meal. Therefore, the presence of high concentrations of residues from antimicrobial drugs in feathers might pose a risk to global public health, due to re-entry of these residues into the food chain. This work aimed to characterise the depletion behaviour of tylosin in feather samples, while considering its depletion in muscle and liver tissue samples as a reference point. To achieve this goal, we have implemented and validated an analytical methodology suitable for detecting and quantifying tylosin in these matrices. Sixty broiler chickens, raised under controlled conditions, received an oral dose of 32 mg kg^-1 of tylosin for 5 days. Tylosin was quantified in muscle, liver and feathers by liquid chromatography coupled with a photodiode array detector (HPLC-DAD). High concentrations of tylosin were detected in feather samples over the whole experimental period after completing both the therapy and the recommended withdrawal time (WDT). On the other hand, tylosin concentrations in muscle and liver tissue samples fell below the limit of detection of this method on the first sampling day. Our results indicate that the WDT for feather samples is 27 days, hence using feather meal for the formulation of animal diets or for other agricultural purposes could contaminate with antimicrobial residues either other livestock species or the environment. In consequence, we recommend monitoring this matrix when birds have been treated with tylosin, within the context of poultry farming.     

Statistical evaluation of residue data for the assessment of predicted values (half-life, withdrawal time) as an example of toltrazuril and enrofloxacin in trout

The half-lives and withdrawal times of the veterinary drugs Toltrazuril and Enrofloxacin in trout have been assessed by statistical analysis. Confidence intervals were computed using a normal distribution of residual data and an empirical distribution by the Bootstrap method. Both methods produced similar statistics for the two drugs. Simulation of the residue data according to the regression lines of the decay curves has shown that the Bootstrap method is better for use when the residue patterns are not distributed normally. Using confidence intervals, a statistical mean of withdrawal times can be assessed. Taking into account the decays of the individual antibiotics in all treated trout, tolerance intervals for the regression lines are obtained: the calculated 10-20% longer withdrawal time includes values for which the antibiotic concentration in 95% of the treated trout is decreased below the tolerance level of Toltrazuril or Enrofloxacin.     

产前饲喂模式下恩诺沙星在初产蛋中的残留规律及膳食暴露评估

目的 消费者长期食用残留恩诺沙星的禽蛋会造成耐药性、过敏反应以及肠道菌群紊乱。本试验旨在探讨蛋鸡产蛋前喂饲恩诺沙星在初产蛋中残留规律,评估其对鸡蛋安全性以及消费者健康的影响。方法 选取378只日龄为85天的海兰褐蛋鸡,根据给药时间分为14组,1.5 g/kg恩诺沙星粉剂,连续拌料喂药 5 d。从给药后生产第 1 枚鸡蛋开始连续采集鸡蛋8天,分析鸡蛋中恩诺沙星及其代谢产物环丙沙星残留量,采用每日允许摄入量对安全性进行评估。结果 初产蛋中恩诺沙星和环丙沙星含量均随着停药时间延长逐渐降低。给药5d,停药1天的初产蛋中恩诺沙星和环丙沙星含最高分别为959.725 mg/kg和62.263 mg/kg,停药7d后鸡蛋中环丙沙星含量低于检出限,痕量恩诺沙星代谢缓慢,停药24d后鸡蛋中恩诺沙星含量低于检出限。停药1d的初产蛋对儿童和成年人身体健康具有慢性危害风险。结论 为了保证禽蛋中无恩诺沙星残留建议至少需要在产蛋前29天用药,停药24天以上,以满足产品符合国家监管以及保证消费者健康的要求。     

Estimating tulathromycin withdrawal time in pigs using a physiologically based pharmacokinetics model

A physiologically based pharmacokinetics model was developed to predict tulathromycin concentrations in edible swine tissues. Physiological parameters included volumes of and plasma flows through different tissues which were obtained from the literatures. The tissue/plasma partition coefficient was calculated according to the area method, and the model was validated through a comparison of predicted and observed concentrations. Withdrawal times in different tissues were predicted. The physiologically based pharmacokinetics model presented here provided accurate predictions of the observed concentrations in all tissues. The results showed that the injection site had the longest withdrawal time (21 days), followed by skin together with fat (19 days) and then kidney (10 days), lung (6 days), liver (4 days) and muscle (1 day). A withdrawal time of 21 days was finally predicted for tulathromycin in swine after a single intramuscular injection at 2.5 mg/kg body weight.     

氟苯尼考在鸡蛋和蛋鸡组织中的残留规律及预测模型建立

氟苯尼考是一种被广泛应用于动物养殖过程中的抗生素药物，可能残留于畜产品中，被人类长期食用会对机体造成耐药性、免疫抑制等不良影响。本实验旨在探讨蛋鸡摄入不同剂量氟苯尼考后，鸡蛋及各组织中氟苯尼考及其代谢产物氟苯尼考胺的清除规律，建立残留预测数学模型。本实验选取处于产蛋高峰期的罗曼粉壳蛋鸡250 只（350 日龄、体质量（1.97±0.07）kg），随机分为5 组，每组50 只，分别给予氟苯尼考0（对照）、30、60、120、240 mg/（kg mb·d），连续给药5 d。采用液相色谱-串联质谱法测定不同休药时间点蛋黄、蛋清、卵黄、肌肉、肝脏中氟苯尼考及其代谢产物氟苯尼考胺的残留含量。结果表明：休药1～3 d时，240 mg/（kg mb·d）剂量组蛋鸡产蛋率与其他处理组相比显著降低（P＜0.05），休药4 d后恢复至对照组水平；氟苯尼考及其代谢产物氟苯尼考胺在产蛋鸡组织中残留含量分布：蛋黄＞卵黄＞蛋清＞肝脏＞肌肉；不同组织残留氟苯尼考及氟苯尼消除所需休药时间：肝脏＜肌肉＜蛋清＜蛋黄＜卵黄；氟苯尼考给药剂量和休药时间对残留含量影响高度显著（P＜0.001），且给药剂量与休药时间互作效应高度显著（P＜0.001）。休药时间、给药剂量和残留含量之间呈现二元二次回归关系（P＜0.001）。为达到《中国兽药典（2015年版）》所规定的氟苯尼考给药剂量范围（40～60 mg/（kg mb·d）），肌肉等组织需休药1 d、蛋清蛋黄需休药13 d、卵黄需休药21 d。     

Simultaneous determination of aminoglycoside antibiotics in milk by liquid chromatography with tandem mass spectrometry

A multiresidue method was developed for determination of nine aminoglycoside antibiotics (streptomycin, dihydrostreptomycin, spectinomycin, neomycin, kanamycin, gentamicin, destomycin A, apramycin, and tobramycin) in milk by LC/MS/MS. The drugs were extracted with 0.01 mol/L potassium dihydrogen phosphate containing 2% trichloroacetic acid, and the extracted solution was cleaned on cation-exchange cartridge columns (Oasis WCX and Oasis MCX). LC separation was performed on a TSK-gel VMpak25 column (50 mmx2.0 mm i.d.) using gradient elution with 0.1% formic acid and acetonitrile containing 0.1% formic acid as the mobile phase. Recoveries of the drugs spiked at 0.01 or 0.1 microg/g in milk ranged from 66.1 to 110.8%, with a coefficient of variation of less than 17.1%. Limits of quantification of the drugs in milk were 0.001 approximately 0.01 microg/g. This method was used for analysis of milk from a lactating cow treated for clinical mastitis with two intramammary infusions of kanamycin (KM). Milk samples were analyzed during the withdrawal times at 12-hour intervals. KM concentrations were lower than the Japanese provisional MRLs (0.4 microg/g) at 60 hours after infusion, and subsequently fell to 0.01 microg/g.     

The residue levels of narasin in eggs of laying hens fed with unmedicated and medicated feed

Laying hens were fed contaminated feed containing narasin 2.5 mg/kg for 21 days followed by a 7 day withdrawal period, hens in the control group were fed unmedicated feed. Eggs were collected during trial days 0, 3, 7, 14, 21 and after the withdrawal period of 7 days. The concentration of narasin in yolks and egg whites was analyzed by a liquid chromatography-mass spectrometry method. Narasin was found to accumulate in yolks, where the narasin concentration increased during the treatment. The concentration of narasin varied from 5.9 to 13.8 microg/kg (mean 10.6 microg/kg) in yolks after 21 day feeding periods. The concentrations of narasin ranged from < 0.9 to 1.4 microg/kg after the withdrawal period. Narasin residues were not found in egg whites of the laying hens fed contaminated feed nor in either yolks or egg whites of the laying hens fed unmedicated feed. The effect of cooking was also tested on the amount of narasin residues in eggs. Cooking for 10 min did not significantly influence the narasin residues in eggs. Traces of lasalocid were also found in the yolks. The traces of lasalocid are attributable to an accidental contamination of the feed during its manufacture.     

Analysis of deoxynivalenol, masked deoxynivalenol, and Fusarium graminearum pigment in wheat samples, using liquid chromatography-UV-mass spectrometry

Tolerable limits set for deoxynivalenol (DON) do not consider DON conjugates such as DON-3-glucoside. Conjugates may be metabolized in vivo to DON. Such masked mycotoxins and the potentially toxic Fusarium pigment are not routinely analyzed in cereals. We quantified DON, DON-3-glucoside, and a red Fusarium pigment in hard red spring wheat, using a new liquid chromatography-mass spectrometry method. Extraction protocols using centrifugation and shaking, and methanol-methylene chloride (50:50 [vol/vol]) or acetonitrile-water (84:16 [vol/vol]) were assessed. Purposively and randomly selected hard spring wheat samples were extracted with solvent filtered through a C18 column and analyzed using liquid chromatography-UV-mass spectrometry. Isocratic mobile phase (70% methanol) was used. Recoveries were 96.4% (DON) and 70.0% (DON-3-glucoside), while limits of detection were 1 microg/kg (MS) and 10 microg/kg (UV), and limits of quantification were 1 microg/kg (UV) and 0.5 microg/kg (MS), respectively. The pigment limits of quantification and limits of detection on the MS were 4.3 and 0.0005 microg/kg, respectively. The purposively selected samples had DON, DON-3-glucoside, and pigment averages of 3.4 +/- 4.0 microg/g, 3.8 +/- 8.3 microg/g, and 0.31 +/- 3.71 g/kg, respectively. The randomly selected spring wheat had lower mean levels of DON (1.4 +/- 2.3 microg/g), DON-3-glucoside (0.2 +/- 1.0 microg/g), and pigment (147.93 +/- 247.84 microg/g). Analytical tools such as this new liquid chromatography-UV-mass spectrometry method can be used to quantify masked and parent mycotoxins, plus a potentially toxic pigment for risk assessment.     

Investigation of the causes for the occurrence of residues of the anticoccidial feed additive nicarbazin in commercial poultry.

Investigations were undertaken to identify causes for the occurrence of high levels of the zootechnical feed additive nicarbazin in broiler liver at slaughter. The first investigation on 32 commercial broiler flocks involved sampling and analysis for nicarbazin (as dinitrocarbanilide, DNC) in liver from birds during a 3-10-day period after withdrawal of nicarbazin from their feed and before commercial slaughter. DNC residues in liver samples of broilers scheduled as being withdrawn from nicarbazin for > or =6 days ranged from 20 to >1600 microg kg(-1) (the specified withdrawal period for nicarbazin is 5 days and the Joint Expert Committee on Food Additives (JECFA) maximum residue limit (MRL) is 200 microg kg(-1) liver). Further on-farm investigations on 12 of these flocks, selected on the basis of the feeding system in use and the levels of DNC residues determined in liver, identified issues in feed management contributing to elevated residues in broiler liver. A significant correlation (0.81, p < 0.01, n = 10) between DNC residues in liver samples and in feed samples from the feeding pans was observed. The second investigation on 12 commercial broiler flocks involved sampling and analysis for DNC in liver samples and feed samples from feeding pans and from the feed mill at the three thinnings of birds for commercial slaughter. In the case of one flock, a clear relationship between nicarbazin in feed from the feed mill (10.5 mg kg(-1) DNC), in feed from the feeding pans (6.6 mg kg(-1) DNC) and in liver (583 microg kg(-1) DNC) at first thinning (9 days scheduled withdrawal from nicarbazin) was observed. Such a clear relationship was not observed in other cases, particularly at second and third thinnings, pointing to re-exposure of birds to nicarbazin late in the flock production cycle, probably from the litter. Guidelines outlining best farm practice to eliminate nicarbazin residues in poultry have been published in booklet and poster format for broiler producers and deal with feed system cleaning, feed bin management, feed deliveries, feed usage and records.     

80%代森锌可湿性粉剂在苹果和土壤中的残留安全性评价

目的评价80%代森锌可湿性粉剂在苹果和土壤中使用后的残留安全性。方法在北京市、安徽省、山东省、辽宁省、宁夏自治区和河南省进行了80%代森锌可湿性粉剂在苹果上的消解动态和最终残留实验。结果代森锌在苹果上的降解半衰期为20.4～36.5 d,最终残留浓度为0.120～3.964 mg/kg;在土壤中的降解半衰期为12.6～15.1 d,最终残留浓度为0.028～3.874 mg/kg。一年6地区监测结果表明,80%代森锌可湿性粉剂防治苹果溃疡病,最高制剂用药量1600 mg/kg,最多施药次数为3次,安全间隔期为28 d。结论在规定最大限度条件下,苹果上代森锌的残留量小于我国规定的食品安全最大允许残留限量5.0 mg/kg,食用苹果是安全的。     

Determination of Enrofloxacin Residues in Commercial Broilers Using High Performance Liquid Chromatography

The broad-spectrum antibacterial drugs are widely used in food producing animals. Suspected residues of these drugs in meat may have ill effects upon human health. The aim of the present study was to determine the enrofloxacin residues in broiler’s meat and liver samples. Detection of enrofloxacin residues in meat (n = 75) and liver (n = 75) samples was performed by high performance liquid chromatography with UV detector set at 268 nm using C₁₈ column. Overall mean residual concentrations of enrofloxacin in meat and liver samples were 208 ± 55 and 527 ± 84 µg/kg, respectively. This study revealed that 52% (39) meat and 78.7% (59) liver samples were positive for enrofloxacin, out of these 58.3% (21) meat and 71.2% (42) liver samples were having residual concentration above the maximum residual limits. So it can be concluded that the usage of this contaminated meat may cause resistance in consumers and seems to be a public health threat.     

In vivo studies to highlight possible illegal treatments of rabbits with carbadox and olaquindox

For the treatment of rabbit dysentery and bacterial enteritis, veterinary practitioners often adopt veterinary medicinal products authorised for other food-producing species, but in some cases non-authorised drugs frequently used in the past, such as carbadox and olaquindox, might be illegally adopted. To verify the carbadox and olaquindox distribution and persistence in rabbit tissues, two independent in vivo studies were carried out. In the first study, 24 healthy rabbits received water medicated with carbadox at 100 mg l^?1 over a period 28 days, whereas in the second one, 24 healthy rabbits were administered water containing olaquindox at 100 mg l^?1. In each study rabbits were randomly assigned to four groups to be sacrificed respectively at 0, 5, 10 and 20 days from treatment withdrawal, for depletion studies. A control group of six animals was adopted for control and as a reservoir of blank tissues. Muscle and liver samples collected from each treated animal were stored at ?20°C pending the analysis. Sensitive and robust liquid chromatography-tandem mass spectrometry analytical methods were set up for the parent compounds and their main metabolites quinoxaline-2-carboxylic acid, desoxycarbadox and 3-methylquinoxaline-2-carboxylic acid to verify their residual. Data collected demonstrate that the combination of liver as target matrix, quinoxaline-2-carboxylic acid and 3-methylquinoxaline-2-carboxylic acid as marker residue and enzymatic digestion is strategic to evidence carbadox and/or olaquindox illegal treatments in rabbits, even 20 days after treatment withdrawal at concentration levels higher than 0.5 µg kg^?1. This findings suggests that liver should be proposed as target matrix for official control in national monitoring plan.