Sorption of tylosin onto swine manure

Sorption of tylosin was conducted on manure solids (<2 mm) and colloidal materials (<1.2 microm) collected from open (OL) and covered (CL) anaerobic swine manure lagoons. The aqueous concentration of tylosin in the sorption studies bracket the levels expected in lagoons, between 1 mgl(-1) and 30 mgl(-1). Sorption isotherms were found to be slightly non-linear for 2 mm solids, with Freundlich distribution coefficients (K(f)) of 39.4 with n=1.32 for CL slurry and 99.5 with n=1.02 for OL. These values are comparable to those reported for loam soils, but higher than those reported for sandy or clay soils and lower than those reported for fresh manure. Normalization of K(d) to the organic carbon content of the solids gave K(oc) values of 570 lkg(-1) and 818 lkg(-1), for CL and OL solids, respectively. The K(d) and K(f) values were not significantly different between colloids and 2 mm solids in OL slurry, but were significantly different in CL due to the non-linearity of the colloid isotherm. Based on the K(d) values obtained and comparing the K(d) values of other antibiotics, tylosin is strongly sorbed to manure, and would be more mobile than tetracyclines, but less mobile than sulfonamides, olaquindox, and chloramphenicol. However, tylosin mobility may be facilitated through transport with colloidal manure materials.     

Degradation and metabolite production of tylosin in anaerobic and aerobic swine-manure lagoons.

Watershed contamination from antibiotics is becoming a critical issue because of increased numbers of confined animal-feeding operations and the use of antibiotics in animal production. To understand the fate of tylosin in manure before it is land-applied, degradation in manure lagoon slurries at 22 degrees C was studied. Tylosin disappearance followed a biphasic pattern, where rapid initial loss was followed by a slow removal phase. The 90% disappearance times for tylosin, relomycin (tylosin D), and desmycosin (tylosin B) in anaerobically incubated slurries were 30 to 130 hours. Aerating the slurries reduced the 90% disappearance times to between 12 and 26 hours. Biodegradation and abiotic degradation occur, but strong sorption to slurry solids was probably the primary mechanism of tylosin disappearance. Dihydrodesmycosin and an unknown degradate with molecular mass of m/z 934.5 were detected. Residual tylosin remained in slurry after eight months of incubation, indicating that degradation in lagoons is incomplete and that residues will enter agricultural fields.