The rate of degradation of enrofloxacin in broiler chicken manure has been characterised. Its degradation was investigated in manure excreted by broiler chickens in an intensively reared chicken facility; further, the degradation also followed after transfer of the excreta into the natural environment occurred. The effect of enrofloxacin and its degradation products on cucumber and tomato was also investigated. Enrofloxacin degradation was shown to take place within the rearing facility and also continuing after the manure was transferred into the environment. The rates of enrofloxacin degradation and the degree of degradation product formation in the manure heap incubated in the environment were condition specific, both variables depending on the manure sampling depth. The degradation half-lives ranged from 12.7 to 38.1 days for enrofloxacin and from 1.2 to 8.2 days for the main metabolite ciprofloxacin. Only the cucumber showed signs of toxicity when incubated with the composted manure immediately after transfer into field occurred (t = 0). No toxic effects to plants were observed when manure from the last incubation day (60th) of the field study and manure from the last incubation day of the laboratory degradation study were applied. The degradation study under field conditions showed that enrofloxacin and its degradation products degrade fast in the environment. Additionally, the toxic effects to plants decrease with the incubation time of manure containing enrofloxacin residuals.
Keywords: Degradation products: desethylene-enrofloxacin, OH-enrofloxacin; Enrofloxacin degradation under environmental conditions; Enrofloxacin degradation within the rearing facility; Enrofloxacin residuals effects to plants; Enrofloxacin residuals toxicity decreases with incubation time; Environmental risk assessment.