ANTIBIOTICS LOSSES IN RUNOFF AND DRAINAGE FROM SWINE MANURE APPLICATION

This study quantified the effect of land application of antibiotic laced swine manure on antibiotic losses in surface runoff and tile drainage. Two antibiotics studied are chlortetracycline and tylosin. Field studies showed very little transport of chlortetracycline and tylosin through Webster clay loam soil into tile drainage. There was almost no transport of dissolved chlortetracycline in surface runoff. Only about 0.07% of the applied tylosin was transported as dissolved tylosin in surface runoff. Laboratory studies showed that these two antibiotics are tightly adsorbed by soils and most of the manure-applied antibiotics are remaining in place where they are applied. However, there is some off-site transport of these antibiotics with sediment in runoff water. Screening of soil samples from Lamberton plots showed that generally soil microbes had no resistance to tetracycline but higher resistance to tylosin after 5 years of swine manure application. There was also more diversity in the resistant bacteria from the manure plots than the urea plots. Similar studies are underway on highly erodibile loess soil in southwestern Wisconsin with swine and beef manure and highly permeable sand y outwash soils in Central Minnesota with turkey and hog manure.