Alum Effects On Veterinary Antibiotics In Runoff From Surface-Applied Broiler Litter.

Georgia is the top broiler-producing state in the USA with a production of 1.3 billion broilers in 2012 and generation of about 1.5 million Mg of broiler litter, most of which is surface applied to grasslands. Surface application of broiler litter leaves it exposed to surface runoff, which may result in surface water contamination with veterinary antibiotics. This study was conducted to evaluate 1) the effect of alum added to surface-applied broiler litter and 2) the effect of time prior to raining on losses of ionophore antibiotics monensin and salinomycin, in surface runoff from grassed plots in the summer and winter seasons. In the summer season, alum reduced total monensin (p-value 0.0010) and total salinomycin (p-value 0.0025) losses, monensin concentration (p-value 0.0262), and salinomycin concentration (p-value 0.0247) compared to unamended litter across all weeks of rainfall simulation. In the winter season, alum did not reduce total monensin (p-value 0.7274), total salinomycin (p-value 0.5466), monensin concentration (p-value 0.9167), or salinomycin concentration (p-value 0.1214) across all weeks. No significant reduction on ionophore amounts or concentration was observed as a function of time for each treatment in either season. Litter+alum maintained lower runoff pH (pH 5.8 to 5.7 vs pH 6.7 to 7.0) compared to unamended litter (summer & winter p-values <0.0001) in both seasons.