Antibiotics have been widely used in poultry production for the treatment of bacterial diseases. However, drug residues can remain in products derived from animals after the cessation of the drug therapies. Feathers, in particular, have shown an affinity for antibiotics such as tetracycline, suggesting the persistence of these drugs in nonedible tissue. After the birds are slaughtered, feathers are ground into feather meals, which are used as organic fertilizer or an ingredient in animal diets, thereby entering into the food chain and becoming a potential risk for public health. To evaluate the depletion of oxytetracycline (OTC) and its metabolite 4-epi-oxytetracycline (4-epi-OTC) in the muscles, liver, and feathers, 64 broiler chickens, bred under controlled conditions, were treated orally with a commercial formulation of 10% OTC for 7 days. The analytes were quantified using liquid chromatography-tandem mass spectrometry. OTC and 4-epi-OTC were found in the feathers for 46 days, whereas they were found in the muscle and liver for only 12 and 6 days, respectively. These results prove that the analytes remain in feathers in higher concentrations than they do in edible tissues after treatment with tetracyclines. Thus, feather meals represent a potential source of antimicrobial residue contamination in the food chain.

Several antimicrobials are routinely used by the poultry farming industry on their daily operations, however, researchers have found for some antimicrobials that their residues persist for longer periods in feathers than they do in edible tissues, and at higher concentrations, as well. But this information is not known for other classes of antimicrobials, such as the sulfonamides. Therefore, this work presents an accurate and reliable analytical method for the detection of sulfachloropyridazine (SCP) in feathers and edible tissues from broiler chickens. This method was also validated in-house and then used to study the depletion of sulfachloropyridazine in those matrices. The experimental group comprised 54 broiler chickens, who were raised under controlled conditions and then treated with a commercial formulation of 10% sulfachloropyridazine for 5 days. Samples were analyzed via LC-MS/MS, using 13C6-sulfamethazine (SMZ-13C6) as an internal standard. Aromatic sulfonic acid solid phase extraction (SPE) cartridges were used to clean up the samples. The Limit of Detection (LOD) for this method was set at 10 μg kg-1 on feathers and liver; and at 5 μg kg-1 on muscle. Within the range of 10–100 μg kg-1, the calibration curves for all matrices presented a determination coefficient greater than 0.96. Our results show, with a 95% confidence level, that sulfachloropyridazine persisted in feathers for up to 55 days after ceasing treatment, and its concentrations were higher than in edible tissues. In consequence, to avoid re-entry of antimicrobial residues into the food-chain, we recommend monitoring and inspecting animal diets that contain feather derivatives, such as feathers meals, because they could be sourced from birds that might have been medicated with sulfachloropyridazine.

Antibiotics are widely used in poultry production for the treatment of bacterial diseases. However, residues may remain in products and by-products destined for human consumption or animal feeding. The claws of chickens, which are a by-product of the poultry industry, can directly or indirectly enter the food chain as meals destined to feed other productive animals. Thus, it becomes necessary to determine and quantify antimicrobial residues present in this matrix. The objective of the study was to assess the depletion of oxytetracycline (OTC) and its metabolite 4-epi-OTC in broiler chicken's claws. Claws of 32 broilers treated with a therapeutic dosage of 10% OTC during 7 days were analysed. Samples were taken at days 3, 9, 15 and 19 post-treatment. As for the control group, eight broiler chickens were raised under the same conditions. Extraction was carried out through EDTA-McIlvaine buffer, and clean-up employed a SPE C-18 Sep-Pak®. Instrumental analysis was performed through LC-MS/MS. The concentrations of both analytes were determined in claw samples until day 19 post-treatment. Average concentrations were within the LOD (20 μg kg) and LOQ (22 µg kg) for OTC and 84 μg kg for 4-epi-OTC. Withdrawal times (WDTs) of 39 days for OTC and 54 days for 4-epi-OTC were established in claws based on 95% confidence. These findings demonstrate that claws can be a source of antimicrobial residue entry into the food chain, since the results showed that OTC and its metabolite can be found in chicken's claws for long periods, even exceeding the average lifespan of a broiler chicken.

A suitable analytical method is required to study the behaviour of florfenicol (FF) and its metabolite florfenicol amine (FFA) in broiler's feathers. An LC-MS/MS method was developed, assessed and intra-laboratory-validated for FF and FFA analyses. We chose cloramphenicol-d as an internal standard, acetone as a solvent for the extraction of the analytes and dichloromethane for the clean-up. Through LC-MS/MS analysis, we established a detection limit of 20 μg kg, as well as calculated quantification limits of 24.4 and 24.5 μg kg for FF and FFA, respectively. Validation parameters such as linearity, recovery and precision were calculated following Commission Decision 2002/657/EC. For linearity, all standard curves showed a standard coefficient greater than 0.99. Recoveries ranged from 99% to 102% for all studied concentrations. The results show that this analytical method is precise and reliable. For the depletion study, 64 Ross 308 broilers were treated with a therapeutic dosage of 10% FF during 5 consecutive days and their feathers were then analysed. Samples were drawn on days 5, 10, 15, 20, 25, 30, 35 and 40 post-treatments. As for the control group, 16 broiler chickens were raised under the same regime. Throughout the whole study, the detected concentrations of FF and FFA in feather samples were above 100 µg kg. In fact, even on day 30 post-treatment we detected concentrations of 221.8 and 28.8 µg kg for FF and FFA, respectively. Based on these results, we conclude that these analytes will persist for a long time and will deplete slowly in feathers of treated broiler chickens.

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 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.