In this literature review we focus on the dispersal of the most frequently used antibiotic classes for veterinary purposes and its residues in the ecosystem."
In summary, antibiotics are poorly absorbed in the gut of animals. As a consequence a large part of the initial compound is excreted. From the application in livestock to manure, the range of excreted antibiotic residues lies between 17-90%. Part of these residues enters the environment through direct application on the field or through run off from the storage. After excretion the residues can also be re-transformed to the initial compound, and thus become active again.
"We thus have to be careful with the administration of veterinary antibiotics and future research has to focus on diminishing the usage of veterinary antibiotics, since more and more bacteria are becoming (multi-)resistant and are causing infections that are harder to treat.