The fate of chlortetracycline residues in a simulated chicken-fish integrated farming systems

Abstract

Two experiments were conducted at the Asian Institute of Technology, Pathumthani, Thailand to investigate the fate of chlortetracycline (CTC) residue in chicken manure and its effect on integrated chicken–fish farming system. During the first experiment, broiler chickens were raised and CTC residues in their manure were analysed. Chicken fed diets containing 0, 50, 200 and 800 CTC mg kg−1 had CTC residue levels of 0, 0.9, 3.8 and 6.5 CTC ng g−1. Once the diet containing CTC was withdrawn, CTC in the manure dropped to negligible amounts (0, 0, 0.2 and 0.5 CTC ng g−1) within 1 day. Integrated chicken–fish farming systems were simulated during the second experiment to determine the fate of antibiotic residues in chicken manure in aquaculture environment. Chickens were fed a CTC-free diet and a feed containing CTC at 200 mg kg−1. Ten 4 m3 square concrete tanks (2 × 2 × 1 m) were used for the experiment. Five tanks were fertilized with CTC-contaminated manure and the remaining five tanks were fertilized with CTC-free manure at a rate of 100 kg dry matter ha−1 day−1. Sex-reversed Nile tilapia (Oreochromis niloticus) was stocked at 12 fish tank−1 on the 14th day after chicken manure application. The immuno-radio microbial receptor assay (Charm II test) revealed that edible fish muscle, fish intestinal tract and sediment were contaminated by CTC at rates of 7.21, 22.104 and 1.788 ng g−1, respectively, after 45 days. Chlortetracycline was detected on day 20 in the water column and gradually increased from 0.26 to 12.13 ng g−1. Chlortetracycline residues were not detected in fish or the aquatic environment of the CTC-free treatment. The results demonstrate the potential for antibiotic residue accumulation in fish and aquatic environment when CTC-contaminated chicken manure is used for pond fertilization.