Antibiotic degradation during manure composting

Area of Science:

• Environmental Science
• Agricultural Science
• Veterinary Pharmacology

Background:

• On-farm manure management, including composting, is explored as a method to reduce antibiotic residues in animal waste before land application.
• Minimizing environmental contamination from veterinary antibiotics is crucial for ecosystem and public health.
• Understanding antibiotic degradation during composting is essential for effective waste management strategies.

Purpose of the Study:

• To quantify the degradation rates of chlortetracycline, monensin, sulfamethazine, and tylosin in spiked turkey litter during composting.
• To compare the efficacy of different composting methods (control, managed pile, vessel) in antibiotic degradation.
• To determine the half-lives of specific antibiotics under composting conditions.

Main Methods:

• Turkey litter was spiked with four veterinary antibiotics: chlortetracycline, monensin, sulfamethazine, and tylosin.
• Three composting treatments were evaluated: a control (undisturbed pile), a managed compost pile (weekly mixing, moisture adjustment), and vessel composting.
• Antibiotic concentrations were measured over a 22-35 day composting period, and degradation rates and half-lives were calculated.

Main Results:

• No significant differences in antibiotic degradation were observed among the control, managed pile, and vessel composting treatments.
• Chlortetracycline showed rapid degradation (>99% reduction, half-life ~1 day), while monensin (54-76% reduction, half-life ~17 days) and tylosin (54-76% reduction, half-life ~19 days) degraded gradually.
• Sulfamethazine exhibited no degradation across all treatments.

Conclusions:

• Managed composting methods (pile or vessel) offer no advantage over simple control (stockpiling) for degrading chlortetracycline, monensin, tylosin, or sulfamethazine in turkey litter.
• Low-level manure management, such as stockpiling with initial water adjustment, may be a practical and economical approach for reducing certain antibiotic levels.
• Composting is not an effective strategy for the complete removal of all veterinary antibiotics from animal manure.