Occurrence and persistence of antibiotics administered to cattle in a newly established feedlot

The practice of using therapeutic and prophylactic veterinary antibiotics in livestock farming is a worldwide phenomenon. Over the last decade, there has been a growing concern of antibiotic residues entering the environment via animal manure. Similar studies have focused on the occurrence and biological effects of antibiotics in land-applied animal feedlots; however, limited research has been conducted on the occurrence and persistence of antibiotics in animal feedlots. Therefore, the objective of this study was to evaluate antibiotic persistence, fate, and transport in surface water runoff and feedlot sediment in feedlot pens with livestock either receiving or not receiving antibiotic treatments through injection and feed. The two antibiotics (tylosin and monensin) added to animal feed were observed to persist in the soil environment for more than 30 days along with injected florfenicol. Monensin (5.6x higher) and tylosin (20x higher) were significantly higher in livestock pens receiving antibiotics compared to livestock pens not receiving the antibiotics. Further, rainfall was observed to significantly impact soil surface concentrations of florfenicol. Other antibiotics administrated by injection were not observed to statistically increase in concentrations in runoff or feedlot sediment. Our findings emphasize antibiotics administered in feedlots have the potential to persist and remain in feedlot sediment and runoff, particularly in instances of regular administration in feed. Occurrence and persistence of paired feedlot pens receiving and not receiving antibiotics were assessed.Antibiotics regularly administered in animal feed were observed to persist in feedlot sediment.Antibiotics administered via injection were observed to persist significantly less in feedlot sediment.

Automated summary

This study evaluated the persistence and impact of antibiotics used in livestock farming on the environment. The results showed that antibiotics added to animal feed could persist in the soil for more than 30 days and could be found in feedlot sediment and runoff. Livestock pens receiving antibiotic treatments had significantly higher concentrations of antibiotics compared to those not receiving treatments. Rainfall also had a significant impact on the concentration of antibiotics in the soil. Antibiotics administered via injection did not significantly increase in concentrations in feedlot sediment and runoff.