Environmental Fate and Transport of Veterinary Antibiotics Derived from Animal Manure

Therapeutic and non-therapeutic uses of veterinary antibiotics are common in concentrated animal feeding operations (CAFOs), resulting in a vast volume of manure with significant presence of antibiotic residues. This review addresses the current usage of veterinary antibiotics in animal agriculture, potential risks from disposing of antibiotic residue-containing animal manure, and the environmental fate and transport of manure-associated antibiotics. To date, more than 150 veterinary antibiotics have been used in animal farms, of which 80% are for non-therapeutic purposes. Most veterinary antibiotics are poorly absorbed in animal bodies, with 30 to 90% of the administered dosage being excreted via urine and feces either as parent compounds or metabolites. In the United States alone, this would lead annually to 18.9 to 56.7 million kg of antibiotic residues inherent in animal manure. Veterinary antibiotic residues are introduced into the environment through land application of animal manure as a nutrient source for crop production. To assess the persistence of antibiotic contaminants in the environment, we summarize the latest literature information to illustrate biotic and abiotic transformation of commonly used antibiotics in manure-containing water and manure-amended soils. The antibiotics, especially those hydrophobic species can interact with soil organic matter (SOM) and soil minerals, thereby limiting their availability for degradation and transport. Combined with our research finding, we discussed concurrent sorption and colloids-facilitated transport of manure-associated antibiotics in field soils. In addition, the uptake and accumulation of veterinary antibiotics in crop plants are also articulated. Considering that veterinary antibiotics may migrate from manure-receiving fields to surrounding water bodies via surface runoff and leaching, we highlighted three mitigation strategies to reduce their load into the environment and minimize their negative effects on agroecosystems.