Fate of tetracycline antibiotics in dairy manure-amended soils

The U.S. dairy industry has changed significantly during the past 20 years. The number of dairies declined 63% from 1997 to 2012 due to the rise in concentrated animal feeding operations (CAFOs) and the concomitant decline of small dairy farms. Efficient and cost-effective dairies adhering to the CAFO business design are praised for their high milk production. However, with a per capita daily manure production of 55 kg, storage and disposal of manure at these large operations pose significant management challenges and environmental risks. Application to surrounding agricultural fields is a common practice for disposing of manure, but the fate and consequences of antibiotics present in dairy waste are issues of great concern. Although antibiotics in the environment promote microbial resistance, their risks to humans and the environment are not completely known. Understanding and predicting the fate of antibiotics from dairy manure in soils is complicated by the variability and complex interactions of soil ...