EFFECT OF FEEDING WET DISTILLERS GRAINS WITH SOLUBLES TO BEEF CATTLE ON AIR AND MANURE QUALITY

Air quality is becoming a pressing issue for beef feedlot producers. Feeding practices influence the excretion of starch, fiber, nitrogen (N), and sulfur (S) in manure, thereby affecting nutrient content and the production of ammonia (NH3) and odorous compounds. Wet distillers grains with solubles (WDGS) are a common and economical ingredient in feedlot diets. WDGS are high in protein, fiber, phosphorus (P), and S but low in starch. The objective of this study was to compare NH3 concentration in the air and nutrients and volatile organic compounds (VOC) concentration in manure between two dietary treatments fed to feedlot cattle. Five pens of feedlot cattle were fed diets containing 14% to 35% WDGS and five pens were fed a corn-based diet with no ethanol byproducts (Control). Each pen had twelve sampling locations (N = 120) where air and manure samples were collected from the feedlot surface. Air samples were analyzed for NH3 concentration. Manure samples were analyzed for dry matter, pH, volatile solids, VOC, and nutrient composition (N, P, and S). Concentrations of P and S in manure and NH3 in the air were higher in pens fed WDGS compared to pens fed the control diet. Concentrations of VOC were similar across both treatments

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Protocols for Nationally Coordinated Laboratory and Field Research on Manure Nitrogen Mineralization

The National Program structure of USDA-ARS provides an opportunity to coordinate research on problems of national and global significance. A team of USDA-ARS scientists is conducting nationally coordinated research to develop predictions of manure N availability to protect water quality and improve farm solvency. Experimental design and research protocols were developed and used in common across all participating locations. Laboratory incubations are conducted at each location with a minimum of three soils, three temperatures, two wetting/drying regimes, and two manure treatments. A soil from the central United States (Catlin silt loam, fine-silty, mixed, superactive, mesic Oxyaquic Argiudoll) is used as an internal reference across all locations. Incubation data are compiled across locations to develop generalized predictions of manure nitrogen mineralization (Nmin). Field validation data are then obtained by monitoring nitrogen (N) transformations in manure-amended soil cores equipped with anion exchange resin to capture leached nitrate. This field data will be used to compare laboratory-based predictions with field observations of Nmin in each soil, climatic zone, and manure type represented. A Decision Support System will then be developed for predicting manure N mineralization across ranges in soil, climate, and manure composition. Protocols used by this research team are provided to 1) document the procedures used and 2) offer others detailed information for conducting research on nutrient transformation processes involving collaboration across locations or complementary research between laboratory and field environments