Effect of feeding wet distillers grains with solubles (WDGS) to growing-finishing cattle on ammonia concentration in air and manure nutrient composition

Air quality is a difficult and pressing problem for feedlot producers. This is compounded by feeding practices that influence the excretion of starch, fiber, crude protein, and sulfur (S) by cattle that significantly affect the production of odorous compounds. Wet distillers grains with solubles (WDGS) are a common and economical ingredient in feedlot diets. WDGS are high in protein, fiber, and S but low in starch. The objective of this study was to compare ammonia (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 14-35% 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.