Poultry litter (PL) is a by-product of broiler production. Most PL is land applied. Land-applied PL is a valuable nutrient source for crop production but can also be a route of environmental contamination with manure-borne bacteria. The objective of this study was to characterize the fate of pathogens, fecal indicator bacteria (FIB), and bacteria containing antibiotic resistance genes (ARGs) after application of PL to soils under conventional till or no-till management. This 2-yr study was conducted in accordance with normal agricultural practices, and microbial populations were quantified using a combination of culture and quantitative, real-time polymerase chain reaction analysis. Initial concentrations of in PL were 5.4 ± 3.2 × 10 cells g PL; sp. was not detected in the PL but was enriched periodically from PL-amended soils. was detected in PL (1.5 ± 1.3 × 10 culturable or 1.5 ± 0.3 × 10 genes g) but was rarely detected in field soils, whereas enterococci (1.5 ± 0.5 × 10 cells g PL) were detected throughout the study. These results suggest that enterococci may be better FIB for field-applied PL. Concentrations of ARGs for sulfonamide, streptomycin, and tetracycline resistance increased up to 3.0 orders of magnitude after PL application and remained above background for up to 148 d. These data provide new knowledge about important microbial FIB, pathogens, and ARGs associated with PL application under realistic field-based conditions.

Confined animal feeding operations can facilitate the spread of genes associated with antibiotic resistance. It is not known how cattle removal from beef cattle backgrounding operation affects the persistence of antibiotic resistance genes (ARGs) in the environment. We investigated the effect of cessation of beef cattle backgrounding operation on the persistence and distribution of ARGs in the beef cattle backgrounding environment. The study was conducted at a pasture-feedlot type beef cattle backgrounding operation which consisted of feeding and grazing areas that were separated by a fence with an access gate. Backgrounding occurred for seven years before cattle were removed from the facility. Soil samples (n = 78) from 26 georeferenced locations were collected at the baseline before cattle were removed, and then one year and two years after cattle were removed. Metagenomic DNA was extracted from the soil samples and total bacterial population (16S rRNA), total Enterococcus species and class 1 integrons ( int I1), and erythromycin ( erm B and erm F), sulfonamide ( sul 1 and sul 2) and tetracycline ( tet O, tet W and tet Q) resistance genes were quantified. Concentrations of total bacteria, Enterococcus spp., class 1 integrons, and ARGs were higher in the feeding area and its immediate vicinity (around the fence and the gate) followed by a gradient decline along the grazing area. Although the concentrations of total bacteria, Enterococcus spp., class 1 integrons and ARGs in the feeding area significantly decreased two years after cattle removal, their concentrations were still higher than that observed in the grazing area. Higher concentrations over two years in the feeding area when compared to the grazing area suggest a lasting effect of confined beef cattle production system on the persistence of bacteria and ARGs in the soil.

Broiler (Gallus gallus) litter fertility regimes and nutrient removal by sorghum-sudangrass [Sorghum bicolor (L.) Moench] are not well defined. The objective of this study was to determine broiler litter fertility regimes for sorghum-sudangrass that would maximize nutrient removal and produce comparable forage nutritive value compared with inorganic fertilizers while reducing potential soil nutrient accumulation. A randomized, complete-block experiment with four replications and four treatments (litter applied at recommended nitrogen [N] rate [Litter-N], recommended phosphorus [P] rate plus supplemental inorganic N [Litter-P1N], recommended P rate [Litter-P], and inorganic fertilizer [INORG]) was established. Acid detergent fiber (ADF), neutral detergent fiber (NDF), crude protein (CP), P, Cu, Fe, and Zn were determined. Treatments did not affect ADF, NDF, Cu, or Fe in 2001, whereas ADF and NDF were similar for INORG and Litter-N in 2002. Greatest P concentrations were observed in Litter-N and Litter-P plots. Crude protein was greatest for INORG plots, similar for Litter-P1N and Litter-N treatments, and lowest for Litter-P plots. Treatments affected Cu and Zn: Forage from Litter-N plots contained 44% greater forage Cu than those from Litter-P plots in 2003. Iron concentration for 2003 was 60% higher than for 2001 in Litter-N plots, and there were 22% and 30% increases in P uptake in 2003 compared with 2001 for the Litter-N and Litter-P1N plots, respectively. Lower rates of broiler litter, applied based on the P requirement and supplemented with inorganic N, can produce similar forage nutritive value to that fertilized with inorganic fertilizer only or broiler litter applied to meet crop N requirements.

Beef cattle backgrounding operations that grow out weaned calves for feedlot finishing contain several environmentally significant constituents. A better understanding of these constituents and their environmental distribution will aid in the development of effective management guidelines for sustainable beef production. This research investigated soil nutrients, bacterial, and veterinary pharmaceutical concentrations across a small backgrounding beef feedlot on a karst landscape. Results indicated that all contaminants were highly concentrated in the feeder area (FD) and were lower in the other feedlot areas. The FD soils had a pH of 8.2, 59 mg kg soil organic matter (SOM), 2002 mg kg soil test phosphorus (STP), 99.7 mg kg NH-N, and 18.3 mg kg NO-N. The other locations were acidic (5.9-6.9 pH) and contained 39 mg kg SOM, 273 mg kg STP, 21.5 mg kg NH-N, and 2.0 NO-N mg kg. Bacteria populations in the FD averaged 2.7 × 10 total cells, 3.9 × 10 spp., 2.9 × 10 spp, and 4.5 × 10 cells per gram of soil. spp. and spp. concentrations were 1 to 4 orders of magnitude lower at the other locations. showed lower dynamic range and was generally uniformly distributed across the landscape. Antibiotic and parasiticide concentrations in the FD were 86.9 ng g monensin, 25.0 ng g lasalocid, and 10.3 ng g doramectin. Their concentrations were 6- to 27-fold lower in the other feedlot locations. Contaminant management plans for this small feedlot will therefore focus on the feeder and nearby grazing areas where soil nutrients, bacteria populations, and veterinary pharmaceuticals were most concentrated.

Adding carbon-rich materials to fields, like manure, may enhance denitrification. Grass filters, which are used to trap surface runoff'from these fields, may also provide a carbon-rich environment that favors water infiltration and denitrification. Nitrous oxide (N20) may be evolved these settings. It is a radiatively important trace gas and intermediate in the denitrification pathway and several other microbial processes. We measured N20 ltux, after simulated rain, using a soil cover technique in poultry-manured plots and grass filters receiving their runoff'. Intact soil cores were used to relate the N20 Ilux to the denitrification potential of the plots. Nitrous oxide fluxes were smaller in grass filters than in manured plots, even though more denitrifying bacteria were present. The average N20 flux in the three most dynamic erosion plots was 755 ttg N20-N m-2h-~, which was 39% of the maximal denitrification rate measured in acetylene-blocked, NO~-amended soil cores. Nitrous oxide flux immediately after rainfall was greater than N20 flux measurements reported for similar agricultural settings.