SYMPOSIA AND ORAL SESSIONS Environment and Management : General Environmental Effects on Poultry

Ammonia (NH3) emission is a major concern for the poultry industry. We hypothesized that fi ber in corn distiller’s dried grains with solubles (DDGS), wheat middlings (WM), and soybean hulls (SH) would lower NH3 emission by increasing bacterial growth in the large intestine, which would 1) repartition N excretion from uric acid to bacterial protein and 2) produce volatile fatty acids that could lower manure pH, slowing bacterial conversion of uric acid to NH3 and shifting the NH3 equilibrium towards less volatile ammonium (NH4). Hy-Line W-36 hens, 45 wk of age, were housed 2 per cage in a randomized complete block design (16 blocks, 2 replications/block). The 4 corn and soybean meal-based diets included a control and experimental diets containing 10% DDGS, 7.3% WM, or 4.8% SH, which contributed equal amounts of neutral-detergent fi ber. Diets contained 2,840 kcal/kg ME, 0.67% digestible TSAA, and 0.71% digestible Lys. Uric acid, Kjeldahl N, pH, and DM contents of fresh manure (n = 32) were measured and NH3 emission was measured over 7 d by placing pooled 24-h manure samples (n = 6) in NH3-emission vessels. Egg production was recorded daily and egg weight measured weekly. Data were analyzed by ANOVA with treatments compared to the control using contrasts. Dietary DDGS, WM, or SH lowered (P ≤ 0.01) 7-d cumulative manure NH3 emission from 3.9 g for the control to 1.9, 2.1, and 2.3 g, respectively, and lowered (P ≤ 0.05) daily NH3 emission rate. The treatments did not affect (P > 0.10) total manure N excretion or uric acid N as a percent of total N, indicating that N excretion was not repartitioned to bacterial protein. However, dietary DDGS, WM, and SH lowered (P ≤ 0.06) manure pH (6.77, 6.80, and 6.85, respectively) compared to the control (7.08). There were no treatment effects (P > 0.10) on egg production or egg mass (egg production × egg weight). Results of this study show that dietary inclusion of 10% DDGS, 7.3% WM, or 4.8% SH lowers NH3 emission from laying-hen manure by up to 50% without affecting egg mass.