Assessment of Antibiotic Residues in Commercial Aquaculture Feeds in Selected Farms in Awka, Anambra State, Nigeria
Abstract
Aquaculture feeds are often compounded with antibiotics to promote growth and prevent diseases in fish. However, the use of antibiotics in aquaculture feeds has raised concerns about the presence of antibiotic residues in fish which subsequently leads to antimicrobial resistance. This study therefore investigated antibiotic residues in Nine (9) different fish feeds used in three selected fish farms located in Awka, Anambra state, Nigeria. One gram (1g) of the feed samples were used for antibiotics residues analysis. The fish feed samples were collected in three replicates each, making it twenty-seven treatment samples. The targeted antibiotics were the commonly used antibiotics which include Tetracycline, Ciprofloxacin, Amoxicillin and Azithromicin. The feed samples were analyzed for antibiotics residues concentration using Uv-Visible Spectrophotometry. The results showed that the mean antibiotic residue concentration from the three farms were higher in the following order; Tetracycline > Ciprofloxacin > Amoxicillin > Azithromicin, with mean concentrations of 85.40±1.78 ug/g, 0.031±0.002 ug/g, 0.019±0.002 ug/g and 0.010±0.001 ug/g respectively. The mean concentration of Tetracycline was higher than the European Union (EU) maximum residue limit of 0.1 ug/g but Ciprofloxacin, Amoxicillin and Azithromicin were all below the EU maximum residue limits of 0.05 ug/g in feed. This study concluded that the analyzed feed samples contained low dose of antibiotics which may contribute to the development of antibiotic-resistant bacteria. It is therefore recommended that antibiotics should not be used in fish feed formulation, so as to help the farmer to make responsible use of antibiotics when there is a genuine need.
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Introduction
Nutrition is a major factor determining the potential of cultured fish to exhibit their genetic capability for growth and reproduction. The increasing costs and limited availability of fish feed have prompted the need for research into alternative feed sources (Ogunkalu, 2019). It is essential to provide cultured fish with sufficient nutritional feed to enhance growth and immunity, ultimately leading to a successful harvest. In order to meet the nutritional requirements of cultured fish, fish feeds are often enriched with additives. Feed additives are dietary ingredients that are incorporated into feed formulations not only for the usual provision of basic nutritional requirements as offered by traditional feed, but also to improve growth, immune responses, and disease resistance in aquatic animals (Onomu and Okuthe, 2024). These additives include probiotics, prebiotics, enzymes, antibiotics, medicinal plants and other feed additives. Antibiotics can be used as feed additives in animal production in order to maintain animal health (Ghimpețeanu et al., 2022). In the aquaculture industry, the health of aquatic animals is of utmost importance in order to ensure optimal production and profitability. Therefore antibiotics have been commonly used to combat diseases and parasites in aquatic animals (Lulijwa et al., 2020). Antibiotics have been included in aquatic feed to prevent or treat bacterial diseases and promote growth (Onomu and Okuthe, 2024). The most often used antibiotics in aquaculture are oxytetracycline, florfenicol, macrolides, fluoroquinolones, and sulfadiazine (Lulijwa et al., 2020).
Conclusion
Antibiotics residues in fish feeds used for aquaculture have become a growing concern due to their potential impact on human health and the environment. This study evaluated the levels of antibiotics residues in nine fish feeds used in three aquaculture farms in Awka, Anambra State. The results revealed that all the nine fish feed samples from the three different fish farms contained varying concentrations of commonly used antibiotics. The result showed that the mean antibiotic residue concentrations were higher in the order; Tetracycline >Ciprofloxacin > Amoxicillin > Azithromycin. It was also observed that Tetracycline had the highest residue concentrations in all the analyzed fish feed samples and this may be as a result of its frequent use in aquacuture feed while Azithromycin had the lowest residue concentrations. The mean concentrations of Tetracycline were higher than the maximum residue limit (MRL) while Ciprofloxacin, Amoxicillin and Azithromycin observed in the fish feed samples were below the MRL. To address this issue, it is recommended that fish farmers should carefully monitor the amount of antibiotics in the feeds they use and practice responsible antibiotic use when necessary. Fish feed producers should also adhere to standards for antibiotics in fish feeds to protect the safety of the food chain and minimize antimicrobial residues. Responsible use of antibiotics in aquaculture under veterinary supervision is crucial to ensure the safety of aquaculture products. Additionally, education and training should be provided to fish farmers on the proper use of antibiotics, including dosage and withdrawal periods, to reduce the risk of antibiotic resistance. Research on novel feed additives, such as the inclusion of probiotics, prebiotics and medicinal plants in fish feeds, should be conducted to reduce feed costs, improve digestibility, and prevent residual effects of antibiotics in fish tissues that may impact human health.