Qualitative determination of tetracycline residues in bovine meat at the level of the municipal slaughterhouse of Santa Rosa Canton, Oro province, EcuadorAbstract
The presence of antibiotic residues in bovine meat is a significant public health concern, particularly in regions with limited regulation of veterinary drug usage. Tetracyclines, commonly used in cattle for therapeutic and prophylactic purposes, can persist in edible tissues if withdrawal periods are not properly observed. This study aimed to qualitatively determine the presence of tetracycline residues in bovine meat from the municipal slaughterhouse of Santa Rosa Canton, El Oro Province, Ecuador. A total of 74 meat samples were collected from the neck muscle of slaughtered cattle. The samples were analyzed using the SmarKit Rapid Test, a qualitative immunoassay designed to detect oxytetracycline, tetracycline, and chlortetracycline residues. Data regarding the age, sex, and origin of the animals were recorded. Statistical analysis was performed using SAS v.9.4, applying descriptive statistics and a Chi-square test to evaluate associations between residue presence and animal variables. Of the 74 samples analyzed, 24 (32.4%) tested positive for tetracycline residues. A significant association was observed between the age of the animals and the presence of residues (P < 0.05), with younger cattle showing higher prevalence rates. No significant correlations were found between residue presence and the sex or origin of the animals. The results highlight gaps in adherence to withdrawal periods and the potential risks to public health from consuming contaminated meat. In conclusions, this study underscores the need for improved veterinary oversight and education for producers on the responsible use of antibiotics in cattle. Additionally, implementing routine screening methods like SmarKit in slaughterhouses can enhance food safety monitoring. Addressing these issues is critical for reducing public health risks and promoting sustainable livestock practices in Ecuador.
Keywords:
tetracycline residues; bovine meat; food safety; public health; SmarKit Rapid Test; Ecuador
Resumo
A presença de resíduos de antibióticos na carne bovina é um problema significativo de saúde pública, particularmente em regiões com regulamentação limitada do uso de medicamentos veterinários. As tetraciclinas, amplamente utilizadas em bovinos para fins terapêuticos e profiláticos, podem persistir em tecidos comestíveis se os períodos de carência não forem devidamente respeitados. Este estudo teve como objetivo determinar qualitativamente a presença de resíduos de tetraciclina na carne bovina do matadouro municipal do Cantão de Santa Rosa, Província de El Oro, Equador. Um total de 74 amostras de carne foram coletadas do músculo do pescoço de bovinos abatidos. As amostras foram analisadas usando o Teste Rápido SmarKit, um imunoensaio qualitativo desenvolvido para detectar resíduos de oxitetraciclina, tetraciclina e clortetraciclina. Dados referentes à idade, sexo e origem dos animais foram registrados. A análise estatística foi realizada utilizando o SAS v.9.4, aplicando-se estatística descritiva e um teste qui-quadrado para avaliar as associações entre a presença de resíduos e as variáveis animais. Das 74 amostras analisadas, 24 (32,4%) testaram positivo para resíduos de tetraciclina. Observou-se associação significativa entre a idade dos animais e a presença de resíduos (P < 0,05), com bovinos mais jovens apresentando maiores prevalências. Não foram encontradas correlações significativas entre a presença de resíduos e o sexo ou a origem dos animais. Os resultados destacam lacunas na adesão aos períodos de carência e os potenciais riscos à saúde pública decorrentes do consumo de carne contaminada. Em conclusão, este estudo ressalta a necessidade de melhor supervisão veterinária e educação dos produtores sobre o uso responsável de antibióticos em bovinos. Além disso, a implementação de métodos de triagem de rotina, como o SmarKit, em matadouros pode aprimorar o monitoramento da segurança alimentar. Enfentar essas questões é fundamental para reduzir os riscos à saúde pública e promover práticas sustentáveis na pecuária no Equador.
Palavras-chave:
resíduos de tetraciclina; carne bovina; segurança alimentar; saúde pública; Teste Rápido SmarKit; Equador
1. Introduction
The presence of antibiotic residues in food products derived from livestock is a growing concern in public health, agriculture, and environmental science (Mendel et al., 2017; Garcia et al., 2019). Antibiotics such as tetracyclines are widely used in veterinary medicine for their broad-spectrum efficacy against bacterial infections, as well as their application in growth promotion and disease prevention in livestock (Mercer, 2022). While their usage has improved animal health and productivity, improper administration, including the failure to observe withdrawal periods, has led to the accumulation of antibiotic residues in edible animal products (Wu and Zeng, 2024), including meat (Vliet et al., 2020). This phenomenon poses serious risks to human health, including the development of antimicrobial resistance, allergic reactions, and disruptions to the gut microbiota (Adesiyun et al., 2007; Maron et al., 2013; FAO, 2021a).Tetracyclines, a group of antibiotics that includes oxytetracycline, tetracycline, and chlortetracycline, are among the most frequently used drugs in animal husbandry (Pokharel et al., 2019). Despite their effectiveness, these compounds can persist in animal tissues if not properly metabolized or if withdrawal times are not adhered to before slaughter. The detection and monitoring of these residues in meat are therefore essential to ensure food safety and protect public health. International organizations such as the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) have highlighted the importance of regulating antibiotic use in livestock and monitoring residues in food products to minimize health risks (FAO, 2021b).
In Ecuador, livestock production plays a significant role in the national economy, particularly in regions such as the El Oro province. Santa Rosa Canton, a prominent agricultural and livestock hub within this province, contributes significantly to the local meat supply (Ecuador, 2022). However, the lack of stringent monitoring mechanisms and insufficient farmer education on the appropriate use of antibiotics pose challenges in maintaining the safety and quality of meat products. Municipal slaughterhouses, such as the one in Santa Rosa, serve as critical points for meat inspection and residue monitoring. Yet, the limited resources and technological capacity at these facilities often hinder effective screening for antibiotic residues.
The presence of antibiotic residues in meat not only threatens consumer health but also raises significant concerns about the environmental impact and sustainability of livestock production (Darwish et al., 2013). Improper disposal of antibiotic-laden animal waste can lead to environmental contamination, contributing to the spread of antimicrobial resistance in soil and water systems. Addressing these challenges requires a multi-faceted approach that includes enhancing veterinary oversight, implementing rapid and cost-effective testing methods, and educating producers on the responsible use of antibiotics (Gilbert et al., 2021).
Several studies conducted globally have demonstrated the utility of rapid detection kits, such as SmarKit, for identifying antibiotic residues in meat (Silva et al., 2023). These tests offer a practical and affordable solution for municipal slaughterhouses with limited access to advanced laboratory facilities (Sriyeni et al., 2022). By utilizing such tools, this study seeks to provide a snapshot of the antibiotic residue issue in Santa Rosa Canton while advocating for scalable solutions that can be implemented across similar contexts in Ecuador and beyond.
Moreover, this investigation contributes to the growing body of research on food safety and public health in the developing world. While much of the literature focuses on high-income countries with robust monitoring frameworks, there is a relative scarcity of studies addressing antibiotic residues in low-resource settings. By focusing on a municipal slaughterhouse in a rural Ecuadorian context, this study provides insights into the challenges and opportunities for improving food safety in similar agricultural systems. Therefore, this study focuses on the qualitative detection of tetracycline residues in bovine meat sourced from the municipal slaughterhouse of Santa Rosa Canton. The primary objective is to assess the prevalence of tetracycline residues in meat samples and identify potential non-compliance with recommended withdrawal periods. The results of this investigation aim to inform stakeholders, including producers, regulatory authorities, and consumers, about the current status of antibiotic residues in local meat products and highlight the need for improved practices and policies.
2. Materials and Methods
2.1. Ethical considerations
All procedures adhered to ethical standards for research involving animals. Sampling was conducted in compliance with national regulations for food safety and animal welfare. The study aimed to minimize waste and ensure that all meat samples used in testing were discarded appropriately after analysis. This methodology provides a reliable and cost-effective framework for detecting tetracycline residues in bovine meat, offering valuable insights into food safety practices at the local level.
2.2. Study area
The study was conducted at the municipal slaughterhouse of Santa Rosa Canton, located in El Oro Province, Ecuador. This facility processes bovine meat intended for local consumption. The region is characterized by its significant agricultural and livestock activity, where antibiotic use is common in cattle production.
2.3. Sample collection
A total of 74 bovine meat samples were collected during routine operations at the slaughterhouse. Samples were taken from the neck muscle of each carcass immediately after slaughter. Each sample was labeled, refrigerated at 4 °C, and transported to the laboratory for analysis within 24 hours to ensure the preservation of residues.
2.4. Detection method
The presence of tetracycline residues was determined using the SmarKit Rapid Test, a qualitative immunoassay specifically designed to detect oxytetracycline, tetracycline, and chlortetracycline residues in meat samples. The procedure included the following steps:
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Sample Preparation: Meat samples (5 g) were homogenized and diluted with a buffer solution provided by the SmarKit manufacturer.
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Extraction: The diluted samples were centrifuged at 3,000 rpm for 10 minutes to separate residues from solid particles.
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Testing: Aliquots of the supernatant were applied to the SmarKit test strips, following the manufacturer’s instructions. Results were read within 10 minutes. A positive result was indicated by a visible line, confirming the presence of tetracycline residues.
2.5. Data recording
Each test result was documented, categorizing samples as “positive” or “negative” for tetracycline residues. Additional data, such as the age, sex, and origin of the animals, were recorded to explore potential correlations between these factors and the presence of residues.
2.6. Statistical analysis
The data were analysed using SAS v. 9.2 statistical software. Descriptive statistics were applied to determine the frequency of positive samples. A Chi-square test was used to evaluate associations between residue presence and variables such as age, sex, and origin of the animals. A significance level of P < 0.05 was considered for all analyses.
3. Results
In the analysis of meat samples from 74 cattle slaughtered at the Santa Rosa slaughterhouse, 24 cases were found to be positive for the presence of tetracyclines in the meat, representing 32.4% of the total, and 50 cases were found to be negative for the test, representing 67.6%, as shown in Table 1.
Regarding to samples according to sex, the analysis of 74 cattle slaughtered at the Santa Rosa showed that there were 49 female and 25 male cattle, representing 66.2% and 33.8%, respectively, as shown in Table 2.
Of 24 positive cases to the test, 15 belonged to females representing 62.5% of the total, and 9 of the positive cases were male bovines representing 37.5%; of the 50 cases that gave negative results, 34 were females representing 68% and 16 were males equivalent to 32% of the negative cases; this relation applied to the Chi-square test gives us a value of 0.219 and a P-value of 0.640 (P greater than 0.05). 219 and a P = 0.640, so it can be said that there is no significant difference between males and females in the result of the test applied, as shown in Table 3.
Distribution of females and males according to their positive or negative tetracycline test result from the laboratory, and their Chi- square test.
The breeds observed in the 74 cattle sampled were Holstein, Mestiza, Brahaman and Brown Swiss with 4, 4, 39 and 27 animals respectively, with percentages equal to 5.4% for Holstein and Mestiza, 52.7% for Brahaman and 36.5% for Brown Swiss, as shown in Table 4.
In Table 5 we observe that there were 24 positive cases to the test, 3 belonged to animals of the Mestizo breed representing 12.5% of the total, 1 case belonged to an animal of the Holstein breed which represents 4.16%, 14 were of the Brahaman breed, equivalent to 58.34%, lastly we have 6 Brown swiss cattle which represent 25% of the animals that were positive to the presence of tetracycline residues in their meat. Finally, 6 Brown Swiss cattle accounted for 25% of the animals that tested positive for the presence of tetracycline residues in their meat; of the 50 cases that gave as negative result we have 3 belonged to animals of the Holstein breed representing 6% of the total, 1 case belonged to an animal of Mestiza breed which represents 2%, 25 were of Brahaman breed which are equivalent to 50%, finally, we have 21 Brown swiss cattle representing 42% of the animals that were negative to the presence of tetracycline residues in their meat (Figure 1).
In addition, the (Table 5) shows the results of the chi-square test which gave us a value of 4.906 and a P-value of 0.179, it can be said that there is no significant difference between the breeds of the animals sampled and the result of the test applied.
Table 6 shows that out of 74 cattle sampled, 15 were 1 to 2 years old, representing 20.3% of the total, 21 cattle were 2 to 3 years old, representing 28.4%, 30 animals were 3 to 4 years old, representing 40.5%, and 8 animals were > 5 years old, representing 10.8% of the total number of animals sampled.
In Table 7 we observe that there were 24 positive cases to the test, 9 belonged to animals from 1 to 2 years old representing 37.5% of the total, 7 were found in an approximate age of 2 to 3 years old representing 29.16%, 8 were around 3 to 4 years old representing 33.34%. Finally, there were no animals older than 5 years that tested positive for the test; of the 50 cases that gave as negative result we have 6 belonged to animals from 1 to 2 years old representing 12% of the total, 14 cases were from 2 to 3 years old representing 28%, 22 estimated an age between 3 to 4 years old which are equivalent to 44%, finally we have 8 animals older than 5 years old representing 16% of the animals that were negative to the presence of tetracycline residues in their meat, attached to this table we have the result of the Chi-square test which gave us a value of 9.505 and a P = 0.023, it can be said that there is a significant difference between the age of the animals sampled and the result of the test applied.
When the survey was carried out in the establishments selling agricultural products in the Santa Rosa canton, the veterinarians in charge were asked to indicate which antibiotic they sold most frequently for larger species, especially for cattle, assigning values from 1 to 6 (6 being the most sold and 1 the least sold); the result was that the main antibiotic sold was Penicillin with 25.17%, in second place we have Tetracycline with 17.01%, in third place we have Streptomycin with 16.32%, in fourth place we have Cephalosporins with 15.99%, in fifth place we have Sulphonamides with a percentage of 15.31% and finally in seventh place we have Erythromycin with 10.20%; these values are detailed in Table 8.
Determination of the medicated antibiotics for major species (cattle) most frequently marketed in agricultural products outlets in the canton of Santa Rosa.
4. Discussion
The increasing prevalence of antibiotic residues in food animal production, particularly in regions such as Ecuador, raises significant public health concerns, especially regarding antimicrobial resistance (AMR) (Cameron and McAllister, 2016). The therapeutic and non-therapeutic use of antimicrobials in food-producing animals has been documented as a crucial factor contributing to the emergence and spread of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) (Mercer, 2022). Similar data were obtained by Olatoye and Ehinmowo (2011) in Nigeria obtaining 28.3% of meat samples with the presence of oxytetracycline; contrasting these results we have Vélez (2013) in Antioquia, Colombia and Gálvez et al. (2018), who practically did not detect the presence of antibiotics in the meat samples analysed, as they obtained 0 and 0.48% of positivity respectively in their studies. A systematic approach to optimizing antibiotic use in both human medicine and animal husbandry is vital to mitigate these risks and ensure the effectiveness of treatments for foodborne diseases. Recent qualitative research involving focus group discussions with non-indigenous backyard food animal producers in Ecuador highlighted the complexities surrounding antibiotic use. These producers often lack access to veterinarians and instead rely on local knowledge and remedies for animal health management, which can lead to suboptimal practices and potential misuse of antibiotics (Ramírez-Telles and Argotti-Rodríguez, 2022). Comparing the results with those obtained by Villa and Vintimilla (2016), we can see that they sampled mostly Holstein cattle with 83.2%, while in this study only 4 samples were analysed from the Holstein breed, equivalent to 5.4% of the total number of samples 4 samples from the Holstein breed, equivalent to 5.4% of the total number of samples were analysed, while Brahaman animals accounted for 52% of the total number of samples. This difference is directly related to the location of the study, since the Villa and Vintimilla (2016) study was carried out in the Azogues canton, province of Cañar, in the Sierra region, where the Holstein breed predominates due to its high milk yield, a characteristic of this particular region (Requelme and Bonifaz, 2012), while in this study carried out on the coast, we have a greater tendency to produce beef cattle, such as the Brahaman breed (Cabezas, 2010; Paredes, 2011). The study emphasized the importance of understanding the perceptions, attitudes, and practices of these small-scale producers to develop more sustainable alternatives to antibiotic use. The data gathered through focus groups and structured observations revealed a need for enhanced education and awareness regarding the implications of antibiotic misuse, particularly among rural populations with limited resources (Silva et al., 2023). Evaluating the data obtained, the presence of a greater number of sampled animals under 5 years of age stands out, (i.e., 89.2%) of the total, which is in line with the research of Villa and Vintimilla (2016) in which they obtained 74%.1% of animals in this category; as for the significance result of the Chi-square test between the variable age and result there is a dissimilarity with the works of Villa and Vintimilla (2016) and Acosta et al. (2014) they obtained a P-value greater than 0.05, therefore it is a result without statistical significance. So, while the global trend in food animal production tends toward intensification and increased antibiotic use to maximize productivity, alternative practices that reduce reliance on antibiotics are emerging among backyard producers (Gilbert et al., 2021). These producers, who operate outside of formal veterinary care systems, often implement their own traditional methods of animal treatment, which may not align with current veterinary recommendations. Thus, their experiences offer valuable insights into potential strategies for sustainable animal health management that do not compromise public health. In this study, a similarity is highlighted with the data obtained by Darwish et al. (2013), where Tetracyclines obtained 41% of predominance before other antibiotics such as β-lactam antibiotics that obtained 18%; but on the contrary we have the work of Cholca, carried out in Cayambe-Santo Domingo, in 2011 (Guatemal and Emerita, 2012), in which Betalactam antibiotics (Penicillins, Aminopenicillins, Cephalosporins) were the most used in dairy cattle with 39%, and with 7% to Tetracyclines (Oxytetracycline). To address the critical public health threat posed by antibiotic residues and AMR, a multifaceted approach is required. This includes enhancing surveillance systems and data collection methodologies to monitor antibiotic use and residues effectively, thereby informing decision-making processes at both local and national levels (Muriuki et al., 2001; Wu and Zeng, 2024). The World Health Organization (WHO) has underscored the importance of preserving antibiotics that are critically important for human health, advocating for responsible use in both human and veterinary contexts (Deatherage, 1957; Founou et al., 2016; Shafqat et al., 2020).
5. Conclusion
The study identified a 32.4% prevalence of tetracycline residues in bovine meat from Santa Rosa's municipal slaughterhouse, highlighting non-compliance with antibiotic withdrawal periods. Younger cattle showed higher residue levels, posing risks to public health, including antimicrobial resistance. These findings emphasize the need for routine residue monitoring, stricter regulatory enforcement, and farmer education on responsible antibiotic use to improve food safety and sustainability in livestock production.
Data Availability Statement
The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request
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Edited by
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Editor:
Ana Paula Peron
