Detection of residues of the coccidiostat diclazuril in poultry tissues by liquid chromatography-tandem mass spectrometry after withdrawal of medicated feed

A facile and intelligent detection method for diclazuril based on a stable dual emissive Eu3+-dopped metal-organic framework

Diclazuril (DIC) is a broad-spectrum anti-coccidiosis drug of the triazine class, widely used in poultry farming. The overuse of DIC may lead to its accumulation in animal bodies, which may enter the food chain and threaten human health. In this work, we fabricated a stable Eu3+-doped UiO-66 fluorescence sensor (EuUHIPA-30) for the sensitive detection of DIC. Among 20 veterinary drugs, the fluorescence of EuUHIPA-30 selectively responds to DIC, with a low detection limit (0.19 μM) and fast response (10 s). EuUHIPA-30 is recyclable and can detect DIC in chicken and eggs with good recoveries. Moreover, a smartphone-integrated paper-based sensor enables the instrument-free, rapid, visual, and intelligent detection of DIC in chickens and eggs. This work provides a promising candidate for practical fluorescent DIC sensing in animal-derived food to promote food safety.

Simultaneous Analysis of Nicarbazin, Diclazuril, Toltrazuril, and Its Two Metabolites in Chicken Muscle and Eggs by In-Syringe Dispersive Solid-Phase Filter Clean-Up Followed by Liquid Chromatography-Tandem Mass Spectrometry

Nicarbazin (NICA) and triazine anticoccidial drugs (diclazuril (DIZ) and toltrazuril (TOZ)) are the primary strategy for preventing and treating coccidiosis. To prevent the development of drug resistance and mitigate the potential chronic toxicity to humans resulting from prolonged exposure, a liquid chromatography-tandem mass spectrometry method with high reliability and sensitivity was developed to determine NICA, DIZ, TOZ, and its two metabolites in chicken muscle and eggs. Upon establishing the extraction conditions involving 10 mL of acetonitrile and 10 min of sonication, in-syringe dispersive solid-phase extraction with silica was performed in combination with n-hexane clean-up. The selection of isotope peaks of precursor ions and low-mass range scanning allowed the two transitions for the quantification of all compounds. The limits of detection for DIZ and NICA were both 0.1 μg/kg, and for TOZ and metabolites, they were 0.3 μg/kg; the limits of quantitation were 0.3 and 1 μg/kg, respectively. The linear range was 0.25-50 ng/mL with a correlation coefficient r > 0.999. The average recoveries at three spiking levels in muscle and eggs were 90.1-105.2% and 94.0-103.7% with the relative standard deviations of 3.0-8.1% and 3.1-14.4%, respectively. The precision, accuracy, and stability were evaluated by three quality control samples.

Development and Application of a Physiologically Based Pharmacokinetic Model for Diclazuril in Broiler Chickens

Withdrawal periods for diclazuril in broilers have traditionally been determined through regression analysis. However, over the last two decades, the physiologically based pharmacokinetic (PBPK) model has gained prominence as a predictive tool for veterinary drug residues, which offers an alternative method for establishing appropriate withdrawal periods for veterinary drugs. In this current study, a flow-limited PBPK model was developed to predict diclazuril concentrations in broilers following long-duration administration via medicated feed and water. This model consists of nine compartments, including arterial and venous plasma, lung, muscle, skin + fat, kidney, liver, intestine contents, and the rest of the body compartment. Physiological parameters such as tissue weights (V_cxx) and blood flow (Q_cxx) were gathered from published studies, and tissue/plasma partition coefficients (P_xx) were calculated through the area method or parameter optimization. Published diclazuril concentrations were compared to the predicted values, indicating the accuracy and validity of the model. The sensitivity analysis showed that parameters associated with cardiac output, drug absorption, and elimination significantly affected diclazuril concentrations in the muscle. Finally, a Monte Carlo analysis, consisting of 1000 iterations, was conducted to calculate the withdrawal period. Based on the Chinese MRL values, we calculated a withdrawal period of 0 days for both recommended dosing regimens (through mediated water and feed at concentrations of 0.5-1 mg/L and 1 mg/kg, respectively). However, based on the European MRLs, longer periods were determined for the mediated feed dosing route. Our model provides a foundation for scaling other coccidiostats and poultry species.

Diclazuril Inhibits Biofilm Formation and Hemolysis of Staphylococcus aureus

Biofilm formation and hemolysis induced by Staphylococcus aureus are closely related to pathogenicity. However, no drugs exist to inhibit biofilm formation or hemolysis induced by S. aureus in clinical practice. This study found diclazuril had antibacterial action against S. aureus with minimum inhibitory concentrations (MICs) at 50 μM for both methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA). Diclazuril (at 1/4× or 1/8× MICs) significantly inhibited biofilm formation of S. aureus under static or flow-based conditions and also inhibited hemolysis induced by S. aureus. The RNA levels of transcriptional regulatory genes (agrA, agrC, luxS, sarA, sigB, saeR, saeS), biofilm formation-related genes (aur, bap, ccpA, cidA, clfA, clfB, fnbA, fnbB, icaA, icaB, sasG), and virulence-related genes (hla, hlb, hld, hlg, lukDE, lukpvl-S, spa, sbi, alpha-3 PSM, beta PSM, coa) of S. aureus were decreased when treated by diclazuril (at 1/4× MIC) for 4 h. The diclazuril nonsensitive clones of S. aureus were selected in vitro by induction of wildtype strains for about 90 days under the pressure of diclazuril. Mutations in the possible target genes of diclazuril against S. aureus were detected by whole-genome sequencing. This study indicated that there were three amino acid mutations in the diclazuril nonsensitive clone of S. aureus, two of which were located in genes with known function (SMC-Scp complex subunit ScpB and glyceraldehyde-3-phosphate dehydrogenase 1, respectively) and one in a gene with unknown function (hypothetical protein). Diclazuril showed a strong inhibition effect on planktonic cells and biofilm formation of S. aureus with the overexpression of the scpB gene.

Carry-over of some Fusarium mycotoxins in tissues and eggs of chickens fed experimentally mycotoxin-contaminated diets

Fusarium mycotoxins are fungal contaminants found in different crops intended for human and animal consumption. Due to the co-occurrence of several of mycotoxins, the present study aimed at examining the transfer of these toxins into tissues of broiler chickens and eggs of laying hens fed contaminated diets. After an adaptation period, the chickens were fed contaminated diets containing mg/kg levels of deoxynivalenol (DON), enniatins (ENN A, A₁, B, B₁) and beauvericin (BEA) and high μg/kg levels of HT-2 toxin (HT-2), T-2 toxin (T-2) and zearalenone (ZEN) during a repletion period of two weeks, followed by a depletion period of two weeks. DON, ZEN, T-2 and HT-2 were not carried out into the skin and the liver of broiler chickens. ENN B (20.5 ± 6.6 μg/kg) and BEA (162 ± 55 μg/kg) were found in the liver, while in the skin their respective concentrations were 50 ± 17 μg/kg and 120 ± 16 μg/kg during the first week of the repletion period. Carry-over rates into liver and skin were higher for BEA (1.6% and 1.2%, respectively) than for ENNs (0.1 and 0.4%, respectively). During the depletion period, ENNs and BEA were eliminated from the skin and the liver. ENN B, ENN B₁ and BEA were carried over into eggs at 0.1%, 0.05% and 0.44% upon 2-3 days of feeding the contaminated diet, respectively. These transfers were fully eliminated 9-10 days after feeding the control diet again. These results indicate the transfer of ENN B, ENN B₁ and BEA from feed to chicken offal, meat products and eggs at a very low degree, thus marginally contribute to the total dietary intake of these fusariotoxins for consumers. Nevertheless, taking precautionary measures in the field, harvest, transport and storage of the raw materials is required to keep the mycotoxin concentration in feed below the safe levels.

Pharmacokinetics, Activity, and Residue Elimination of R- and S-Diclazuril in Broiler Chickens

Diclazuril (DIC) is widely used as a racemic mixture to prevent and treat coccidiosis in farm animals, while the pharmacokinetics, bioactivity, and toxicity of DIC enantiomers are not known at all. This study first established a simple, sensitive, and reliable liquid chromatography tandem mass spectrometry method for separation of R-DIC and S-DIC and their analyses. Then, it was applied to investigate the stereoselective pharmacokinetics and residual elimination of individual enantiomers, and their anticoccidial activity was also evaluated in broiler chickens. The results indicated that the area under the concentration-time curve (AUC) and elimination half-life (t_1/2β) were significantly different (p < 0.05) for two enantiomers in chicken plasma. The AUC and t_1/2β of S-DIC were approximately 2 and 1.4 times those of R-DIC, respectively. The residual elimination of DIC enantiomers in chicken tissues was also stereoselective. The concentrations of S-DIC in chicken muscle and liver were greater than those of R-DIC, and it is the opposite in the kidney. There was no significant difference (p > 0.05) in the anticoccidial activity of racemate and enantiomers when a single enantiomer in feed was added above 0.5 mg kg^-1. However, the anticoccidial activity of R-DIC (0.25 mg kg^-1) was significantly higher (p < 0.05) than that of S-DIC (0.25 mg kg^-1) in the diet. It should be mentioned that in chicken small intestine and cecum, the enantiomerization rate of each enantiomer in the infection group was faster than that in the uninfected group.

Multiple response optimization of a QuEChERS extraction and HPLC analysis of diclazuril, nicarbazin and lasalocid in chicken liver

A method for the simultaneous determination of three commonly used coccidiostats in chicken liver was developed, comprising a multi-residue QuEChERS (quick, easy, cheap, effective, rugged and safe) extraction step, and a liquid chromatography-ultra violet-fluorescence (HPLC-UV/FL) analysis. The QuEChERS extraction was optimized using an experimental design approach that includes a screening step to obtain the critical variables, an optimization step using multiple response surface analysis and the calculation of a desirability parameter. The optimized method was validated with fortified samples, reaching an average recovery of 91% and an overall precision of 5.5% (mean of three analytes at three levels). Limits of detection calculated on fortified samples were 20 µg kg^-1 for lasalocid, 15 µg kg^-1 for nicarbazin and 120 µg kg^-1 for diclazuril. These values resulted at least one order of magnitude lower than the maximum allowed residue limit (MRL) of the studied coccidiostats for chicken liver.

Metabolism, Distribution, and Excretion of Ethanamizuril in Chickens

Ethanamizuril(N-{4-[4-(3,5-dioxo-4,5-dihydro-3H-[1,2,4]triazin-2-yl)-2-methyl-phenoxy]-phenyl}-acetamide, EZL) is a new anticoccidiosis compound and belongs to the class of triazines. In this study, the metabolism, distribution, and excretion of EZL were evaluated in chickens after administration of EZL at a single dosage. According to the relevant drug biotransformation rules, the exact molecular mass detection, the fragmentation characteristics, and the retention times, a total of five metabolites were identified in vivo in chickens, including two phase I metabolites and three phase II conjugated metabolites. The major metabolic pathways of EZL in chickens were deacetylation, hydroxylation, and glucuronidation. Regarding ¹⁴C-tissue residues after administration, kidney was considered to be the target tissue, as ¹⁴C-tissue residues could be detected at 240 h postdose. DeacetylEZL (M3) was the main metabolite, accounting for 68.65% and 25.62% of ¹⁴C in kidney at 6 and 24 h, respectively. In heart, muscle, skin+fat, and lung tissues, EZL was the main radioactive substance accounting for 94.88%, 97.32%, 96.23%, and 91.3% of ¹⁴C, respectively. In the liver, EZL and M3 were 20.76% and 54.65% of ¹⁴C, respectively. In chicken tissues the ratio of M5 was too low to be quantitated and it was mainly detected in chicken fecal and bile samples. In chicken excreta, EZL, M3, and glucuronidation of EZL (M5) accounted for 7.02%, 12.33%, and 10.32% of the dose, respectively and were eliminated primarily. This study presents the first detection of EZL metabolites, which is helpful for further understanding of the metabolic mechanism and in vivo intermediate processes of EZL. The results of this study will be good bases for better understanding EZL's anticoccidiosis mechanism and will serve as a helpful reference for assessing the risks to animals and humans.

HPLC semi-preparative separation of diclazuril enantiomers and racemization in solution

Diclazuril has been widely used in poultry feed for prevention and treatment of coccidiosis, and its chiral separation is rarely reported. Herein, semi-preparative separation method of diclazuril enantiomers has been developed through normal-phase high-performance liquid chromatography. Effects of chiral stationary phases, alcoholic modifiers, and column temperature on separation of diclazuril were discussed in detail. Both the single-urea-bound 4-chlorophenylcarbamoylated β-cyclodextrin and amylose tris(3,5-dimethylphenylcarbamate)-coated chiral stationary phases showed strong ability in separation of diclazuril by using n-hexane-trifluoroacetic acid-ethanol. Then, semi-preparative separation of diclazuril was carried out through stacked injection, and the "enantiomeric excess" purities of two fractions were over 98%. Next, the electronic circular dichroism profiles of these two fractions in ethanol solution displayed the mirror image of each other in the range 360-200 nm. Moreover, effects of acidic/basic additive, time, and temperature on racemization of diclazuril enantiomers in ethanol solution have been studied in detail through normal-phase high-performance liquid chromatography. Racemization of diclazuril enantiomers was remarkably accelerated through adding triethylamine at high temperature. We envision that this systematic investigation of diclazuril at an enantiomeric level would provide valuable information in future studies involving enantioselective bioactive, metabolic, and toxicological activities.

Rapid and sensitive detection of diclazuril in chicken samples using a gold nanoparticle-based lateral-flow strip

In this study, we produced a sensitive and specific monoclonal antibody (mAb) against diclazuril based on a new hapten. The mAb, which belongs to the IgG2 subclass, had a 50%-inhibitory concentration of 0.36 ng/mL. A cross reactivity test revealed that the mAb had good specificity for diclazuril. A gold nanoparticle-based lateral-flow strip was assembled for the rapid screening of diclazuril in raw chicken breast and thigh samples. The strip assay had a visual limit of detection (LOD) of 2 μg/kg and a cut-off value of 20 μg/kg for diclazuril in chicken samples when evaluated with the naked eye. With the aid of a strip scan reader, the proposed assay obtained a quantitative measurement for diclazuril with an LOD of 1.08 μg/kg. Therefore, this gold nanoparticle-based lateral-flow strip assay represents a potentially useful tool for on-site detection and rapid initial screening of diclazuril in chicken samples.

Protective potential of diclazuril-treated oocysts against coccidiosis in layer chicks

Diclazuril, which is widely used for the prevention of coccidiosis in chickens, has a lethal effect on asexual and sexual stages of Eimeria spp. However, little is known about its effect on the exogenous stages of Eimeria spp. In this study, we evaluated the effect of in vitro treatment with 0.2% diclazuril on unsporulated and sporulated oocysts of Eimeria spp. For this purpose, a total of 180 male layer chicks aged one day were randomly divided into 5 experimental groups. Each group was divided into 3 replicates of 12 chicks each. Group 1 (G1) and Group 2 (G2) were negative (non-immunized and non-challenged) and positive (non-immunized and challenged) controls, respectively. Group 3 (G3) was immunized per os with 1.0 × 10⁴ non-diclazuril treated-sporulated oocysts. Groups 4 (G4) was immunized per os with 0.2% diclazuril treated-unsporulated oocysts (1.0 × 10⁴) in which diclazzuril didn't affect sporulation. Group 5 (G5) was immunized per os with 0.2% diclazuril treated-sporulated oocysts (1.0 × 10⁴). Chicks of G2, G3, G4, and G5 were challenged with 7.5 × 10⁴ untreated sporulated oocysts at the age of 21 days, while the group 1 chicks remained unchallenged. G4 and G5 animals immunized with 0.2% diclazuril-treated oocysts showed a significant decrease in bloody diarrhea severity, lesion scores, and oocyst counts in comparison to those immunized with untreated oocysts. Furthermore, histopathologic findings showed a low number of parasitic stages in cecal tissues in G4 and G5. A significant increased body weight gain was observed in Gs 4 and 5 in comparison to G2. In addition, expression levels of IL-2, IL-12, and IFN-γ were significantly increased in G4 and G5. In conclusion, diclazuril is effective in attenuating Eimeria oocysts and thus provides an alternative approach for using diclazuril-treated oocysts to protect chicks against Eimeria challenge.

Determination of residual enantiomers of diclazuril in chicken edible tissues by high performance liquid chromatography

A convenient, simple, selective and reliable method was established for separating diclazuril enantiomers and detecting their residues in chicken edible tissues by using high-performance liquid chromatography. The potential effects of chiral column, mobile phase and column temperature on chiral separation of racemic diclazuril were evaluated. Average recovery rates of R-diclazuril and S-diclazuril in three spiking levels ranged from 84.3% to 109.5%, and the relative standard deviations were <15.8%. The limits of quantification of two enantiomers were all 25 ng g^-1 in all chicken tissues. The method proposed was successfully applied to monitor distributions and residue elimination of diclazuril enantiomers in chicken muscle, liver, kidney and fat following oral administration. There are no obvious differences (p > 0.05) between R-diclazuril and S-diclazuril in the same tissue for each sampling time. The elimination rates in liver were the fastest and the residual time in kidney was the longest. These results can help further evaluate pharmokinetics, pharmodynamics and toxicity of each enantiomer of diclazuril in food-producing animals.

Coccidiostats in milk: development of a multi-residue method and transfer of salinomycin and lasalocid from contaminated feed

A confirmatory multi-residue method was developed for the determination in milk of 19 coccidiostats (amprolium, arprinocid, clazuril, clopidol, decoquinate, diclazuril, ethopabate, halofuginone, lasalocid, maduramicin, monensin, narasin, nicarbazin, nequinate, robenidine, salinomycin, semduramicin, toltrazuril sulfone and toltrazuril sulfoxide). Sample preparation utilising extraction with organic solvent and clean up by SPE and freezing was found reliable and time-efficient. Optimised chromatography and MS conditions with positive and negative ESI achieved sufficient sensitivity and selectivity. Validation experiments has proven method usefulness for routine analysis of coccidiostats in milk samples. An on-farm study conducted on dairy cows fed with experimentally contaminated feed with salinomycin and lasalocid showed negligible transfer to milk. No residues of lasalocid were found in collected samples. Salinomycin was found only in 5 of 168 samples analysed, while the concentrations of salinomycin in those samples (0.119-0.179 µg kg^-1) was significantly below the limit of salinomycin in milk set by European Union legislation. Such low concentrations of both coccidiostats cannot be explained by conjugation during dairy cows' metabolism, as shown by experiments with enzymatic hydrolysis.

Distribution of Flunixin Residues in Muscles of Dairy Cattle Dosed with Lipopolysaccharide or Saline and Treated with Flunixin by Intravenous or Intramuscular Injection

Twenty dairy cows received flunixin meglumine at 2.2 mg/kg bw, administered once daily by either the intravenous (IV) or intramuscular (IM) route for three consecutive days with either intravenous normal saline (NS) or lipopolysaccharide (LPS) providing a balanced design with five animals per group. Cows were sacrificed after a 4 day withdrawal period, and 13 muscle types were collected and assayed for flunixin by LC-MS/MS. After elimination of sample outliers, the main effects of route of administration (IV or IM), treatment (NS or LPS), and tissue type significantly (P < 0.05) affected flunixin residues, with no interaction (P > 0.05). Intramuscular (nonlabel) flunixin administration produced greater (P < 0.05) flunixin residues in muscle than the IV (label) administration, whereas LPS resulted in lower flunixin levels. Differences among the tissue levels indicate it is necessary to specify the tissue to be used for any monitoring of drug levels for consumer protection.

Control of eight predominant Eimeria spp. involved in economic coccidiosis of broiler chicken by a chemically characterized essential oil

AIM

To control eight most predominant Eimeria spp. involved in the economic disease of coccidiosis in broiler chicken, by a chemically characterized essential oil of eucalyptus and peppermint.

METHODS AND RESULTS

The experimental design consisted of 160 day-old-broiler chicks, divided into four equal groups (G1 , G2 , G3 and G4 ), with 40 birds per group. Each group was divided into four equal subgroups. Birds in G1 were deprived of essential oil treatment and of Eimeria challenge. Birds in G2 were unchallenged, and administered the essential oil in drinking water at 0.69 ml kg(-1) body weight. Birds in G3 were untreated with essential oil, and each of its four subgroups was challenged at a different age (14, 21, 28 and 35 days). Birds in G4 were treated with essential oil, and challenged in the same manner as for G3 . Equal number of birds from all subgroups (n = 10) were sacrificed at the sixth day after the time allocated for each challenge. The 6 day incubation period post challenge resulted in respective mean per cent weight increase in G2 and G1 birds equivalent to 57.8 and 53.1% (P < 0.05). In addition, the essential oil improved the per cent weight increase in challenged birds (54.6%) compared to the challenged-untreated birds (18.6%) (P < 0.05). The mean feed conversion, mortality, intestinal lesion scores and oocyst counts were significantly reduced in the challenged-treated birds compared to the challenged-untreated birds (P < 0.05).

CONCLUSIONS

The results support the hypothesis of using the essential oils of eucalyptus and peppermint to control the most prevalent Eimeria spp. involved in coccidiosis of broiler chicken, helping in improvement of their production, alleviation of lesions and reduction in intestinal oocyst counts.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides information about the possibility of using this blend of essential oil as a coccidiostat for the protection of broiler chickens against the prevalent eight Eimeria spp. of coccidiosis.

Review: Chinese herbs as alternatives to antibiotics in feed for swine and poultry production: Potential and challenges in application

Gong, J., Yin, F., Hou, Y. and Yin, Y. 2014. Chinese herbs as alternatives to antibiotics in feed for swine and poultry production: Potential and challenges in application. Can. J. Anim. Sci. 94: 223–241. Traditional Chinese medicine (TCM) has a long history of clinical practice, and its own theoretical framework focused on functions at the whole-body level. However, due to cultural differences, TCM has not been fully recognized in Western countries. With the recent development of the theory of whole-body systems biology and “-omics”, there is a new opportunity to study TCM and to close the gap between TCM and Western medicine, because of the similarity in the theoretical foundations between TCM and whole-body systems biology. The uniqueness of TCM theory and practice is the approach to maintain and restore the body balance as a whole with no or little unfavourable side effects. Recent studies have also shown that Chinese herbs used as feed additives can modulate nutritional metabolism, immune responses, and intestinal health of food-producing animals, demonstrating good potential as substitutes for dietary antibiotics. Nonetheless, some issues need to be addressed before Chinese herbs can reach their full application. This article has critically reviewed recent progresses in scientific research of Chinese herbs as feed additives and their potential to replace dietary antibiotics. Possible challenges in future application for swine and poultry production are also discussed.

Transfer of flubendazole and tylosin from feed at cross-contamination levels to various poultry matrices

Residues of veterinary drugs and feed additives used extensively in animal husbandry are sometimes found in edible matrices. In this study, broilers received experimental feed, containing either flubendazole or tylosin, at cross-contamination levels of 2.5%, 5%, and 10% of the therapeutic dose to determine the transfer ratio of these molecules from feed to poultry matrices. Breast and thigh muscle and liver samples were collected during treatment and depletion periods and then analyzed using liquid chromatography-tandem mass spectrometry. The parent molecule flubendazole and its 2 major metabolites were quantified. After 3 to 5 d, a plateau phase was reached, and a few days after withdrawal of the experimental feed, a depletion of residues was noted. Significant difference between both muscle types was noted for flubendazole. Strong metabolization of flubendazole in the liver was seen. For tylosin, no residue concentrations above the limit of quantification could be detected in muscle. None of the residue concentrations for either molecule exceeded the corresponding maximum residue limits.

Risk assessment of coccidostatics during feed cross-contamination: animal and human health aspects

Coccidiosis, an intestinal plasmodium infection, is a major infectious disease in poultry and rabbits. Eleven different coccidiostats are licensed in the EU for the prevention of coccidiosis in these animal species. According to their chemical nature and main biological activity, these compounds can be grouped as ionophoric (monensin, lasalocid sodium, salinomycin, narasin, maduramicin and semduramicin) or non-ionophoric (robenidine, decoquinate, nicarbazin, diclazuril, and halofuginone) substances. Coccidiostats are used as feed additives, mixed upon request into the compounded feed. During the technical process of commercial feed production, cross-contamination of feed batches can result in the exposure of non-target animals and induce adverse health effects in these animals due to a specific sensitivity of mammalian species as compared to poultry. Residue formation in edible tissues of non-target species may result in unexpected human exposure through the consumption of animal products. This review presents recent risk assessments performed by the Scientific Panel on Contaminants in the Food Chain (CONTAM) of the European Food Safety Authority (EFSA). The health risk to non-target species that would result from the consumption of cross-contaminated feed with coccidostats at levels of 2, 5 or 10% was found to be negligible for most animal species with the exception of salinomycin and monensin in horses because of the particular sensitivity for which toxicity may occur when cross-contamination exceeds 2% and 5% respectively. Kinetic data and tissue analyses showed that residues of coccidiostats may occur in the liver and eggs in some cases. However, the level of residues of each coccidiostat in edible animal tissues remained sufficiently low that the aggregate exposure of consumers would not exceed the established acceptable daily intake (ADI) of each coccidiostat. It could be concluded that technical cross-contamination of animal feeds would not be expected to adversely affect the health of consumers.

Distribution of penicillin G residues in culled dairy cow muscles: implications for residue monitoring

The U.S. Food and Drug Administration sets tolerances for veterinary drug residues in muscle but does not specify which type of muscle should be analyzed. To determine if antibiotic residue levels are dependent upon muscle type, seven culled dairy cows were dosed with penicillin G (Pen G) from 1 to 3 days and then sacrificed on day 1, 2, or 5 of withdrawal. A variety (9-15) of muscle samples were collected, along with liver and kidney samples. In addition, corresponding muscle juice samples were prepared. All samples were extracted and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine Pen G levels. Results showed that Pen G residue levels can vary between and within different muscles, although no reproducible pattern was identified between cows or withdrawal times. Muscle juice appeared to be a promising substitute for muscle as a matrix for screening purposes. Because of the potential for variation within muscles, all samples taken need to be large enough to be representative.

Antibiotic residues distribute uniformly in broiler chicken breast muscle tissue

Use of antibiotics by the poultry industry has the potential to produce residues in edible tissues. In order to protect consumers, the U.S. federal government performs extensive evaluations to quantify residues in edible tissues to ensure that concentrations do not exceed the tolerance level. However, in the case of muscle tissue, the regulatory process does not differentiate between different edible muscle types in poultry. Previous studies performed by our laboratory determined higher fluoroquinolone residue concentrations in breast versus thigh muscle. Thus, if thigh tissues were used for residue monitoring, it would not accurately depict the higher concentrations. It is also possible that residue concentrations vary within tissues. To evaluate this possibility, fluoroquinolone antibiotic residues were determined for different breast sections. One hundred sixty chickens were randomly divided into four groups and dosed at 33 days of age with the fluoroquinolone antibiotic, enrofloxacin (Baytril), at either 25 ppm for 3 days, 25 ppm for 7 days, 50 ppm for 3 days, or 50 ppm for 7 days. Breast fillets were collected from each bird (n = 5 birds per day per group) during the dosing and withdrawal period. Each breast was divided into four sections (upper left, upper right, lower left, and lower right) that were analyzed as individual samples for determination of fluoroquinolone concentration. Our results indicated no significant difference (P > 0.05) in the levels of enrofloxacin residues between breast sections during the dosing or withdrawal periods. Consequently, samples can be collected from any breast section to evaluate fluoroquinolone residue concentrations during the regulatory monitoring process.