Rainfall Timing Effect On Concentrations of Testosterone and Estradiol in Surface Runoff From Broiler Litter Applied to Grassed Plots.

Broiler litter contains the sex hormones testosterone and estradiol, which may contaminate surface runoff following litter application to grasslands.  This study was conducted to evaluate the effect of runoff occurring at different times after litter application and under different environmental conditions on the concentrations of estradiol and testosterone in surface runoff from grassed plots.  Thirty two plots (0.75 x 2 m) were established on a tall fescue/bermudagrass pasture.  Treatments consisted of rainfall simulation at 0, 1, 2 or 4 weeks after broiler litter application at 6.5 Mg/ha.  A control treatment without litter application was also included and all treatments were replicated four times. Simulated rainfall was applied at 50 mm h^-1 and all runoff was collected for 30 min after runoff started. The total runoff collected was weighed, mixed thoroughly, and a subsample was analyzed for estradiol and testosterone concentrations by GC/MS. To prevent natural rainfall from reaching the plots, a transparent cover was placed on each plot during the four weeks of the study and was only removed during rainfall simulations.  This cover was mounted on 40-cm legs so that air was able circulate below the cover to prevent excessive heat buildup.  The study was carried out in Aug-Sep 2008 and repeated in Feb 2009 after a second application of broiler litter. In the Aug-Sep study, the difference in average hormone concentrations between litter-treated and control plots was 160 ng testosterone/L and 40 ng estradiol/L.  In the February study, the difference in average concentrations between litter-treated and control plots was 360 ng testosterone/L and 70 ng estradiol/L.  Differences between litter-treated and control plots persisted throughout the four weeks of each study.