Supplements and growth promotants containing steroid hormones are routinely administered to beef cattle to improve feeding efficiency, reduce behavioral problems, and enhance production. As a result, beef cattle manure will contain both synthetic steroids as well as a range of endogenous steroids including androgens, estrogens, and progestogens. A two-year controlled study was conducted in which beef cattle were administered steroid hormones via subcutaneous implants and feed additives and the occurrence of 16 endogenous and synthetic steroid hormones and metabolites was evaluated in runoff from beef cattle feedlots and in manure and soil collected from feedlot surfaces. Samples were extracted and analyzed using liquid chromatography tandem mass spectrometry for metabolites of the synthetic androgen trenbolone acetate, 17α-trenbolone, 17β-trenbolone, for the nonsteroidal semisynthetic estrogen agonist, α-zearalanol, and the synthetic progesterone melengesterol acetate, as well as a wide range of endogeneous estrogens, androgens, and f usarium metabolites. Synthetic steroids including trenbolone metabolites and melengestrol acetate were detected in fresh manure and in feedlot surface soils from cattle administered synthetic steroids at concentrations up to 55 ± 22 ng/g dry weight (dw) (17α-trenbolone) and 6.5 ± 0.4 ng/g dw (melengesterol acetate). Melengesterol acetate was detected in 6% of runoff samples from feedlots holding cattle administered synthetic steroids at concentrations ranging up to 115 ng/L. The presence of melengesterol acetate in runoff from beef cattle feeding operations has not been previously reported. Synthetic steroids were not detected in manure or runoff from control cattle. A wide range of endogenous hormones were detected in runoff and feedlot surface soils and manure from cattle given synthetic steroids and from control cattle, with no statistically significant differences in concentration. These results indicate that runoff from confined animal production facilities is of environmental and public health concern regardless of the use of growth promotants.

No abstract

No abstract

No abstract

Implications of corn (Zea mays l.) residue grazing and baling on wind erosion in integrated crop-livestock systems are not well understood. This study (i) determined soil properties affecting wind erosion potential including dry aggregate-size distribution, geometric mean diameter (GMD), geometric standard deviation of dry aggregates, and wind-erodible fraction (WEF), (ii) correlated these properties with soil organic C (SOC) and particulate organic matter (POM), and (iii) simulated soil loss using the Single-event Wind Erosion Evaluation Program (SWEEP) model after 7 and 8 yr of irrigated no-till corn residue management in a semiarid region in west-central Nebraska. residue treatments were: control (no residue removal), light grazing (2.5 animal unit months [AUM] ha −1 ), heavy grazing (5.0 AUM ha −1 ), and baling. We simulated soil loss for a 3-h windstorm with a wind velocity of 13 m s −1 . Soil properties differed in spring but not in fall. Baling reduced 6.3-to 45-mm macroaggregates by 37% and GMD by 80% and increased WEF by 25% relative to the control. light and heavy grazing, after 8 yr, significantly reduced 6.3-to 14-mm macroaggregates 43% compared with the control and tended to reduce GMD and increase WEF, although not statistically significant. As residue cover decreased, GMD decreased and WEF increased. residue removal did not reduce SOC and POM concentrations, but soil erodibility decreased as POM increased. Simulation showed that soil erodibility increased as residue cover decreased in spring, and baling increased the wind erosion potential. Overall, residue baling increases the wind erosion potential but residue grazing has smaller effects in this semiarid environment.Abbreviations: AUM, animal unit month; GMD, geometric mean diameter of dry aggregates; GSD, geometric standard deviation; SOC, soil organic carbon; POM, particulate organic matter; WEF, wind-erodible fraction. C orn residues provide numerous services for crop and livestock production, biofuel production, protection of soil, and environmental quality. For example, corn residues are considered an inexpensive cattle feed source in times when the availability of forage is limited. Residues are grazed by livestock, baled as animal feed, and mixed with ethanol co-products (i.e., distillers grains) for cattle feed. Corn residues are also potential feedstocks for the production of secondgeneration biofuels. The long-term impacts of grazing and baling of corn residues on soil services have not yet been fully investigated (Nelson et al., 2015).One of the services that should be further considered prior to residue removal is wind erosion control. Particularly in semiarid regions such as the central Great Plains, the presence of abundant crop residue cover is essential for controlling wind erosion. Recent estimates have shown that removal of corn residues at rates as low as 10 to 30% could increase the risks of wind erosion in semiarid regions, depending on the amount of residue produced (Miner et al., 2013 Core Ideas• Corn residue baling incre...