Effects of dietary fiber and low crude protein on manure ammonia emission and egg production in laying hens

Roberts, Stacey
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Ammonia (NH₃) emission is a major concern for the poultry industry. We hypothesized that fiber in corn distiller's dried grains with solubles (DDGS), wheat middlings (WM), or soybean hulls (SH), when included in laying-hen diets, would lower manure NH₃ emission by repartitioning nitrogen excretion from uric acid to bacterial protein and by lowering the pH of the manure. Additionally lower dietary crude protein would result in lower NH₃ emission by decreasing uric acid excretion. From 23 to 58 weeks of age, laying hens were fed 8 dietary treatments with 2 contents of CP (normal and low) and 4 fiber treatments including a corn- and soybean meal-based control diet and diets formulated with 10% corn DDGS, 7% WM, or 5% SH added to contribute equal amounts of neutral-detergent fiber. The low crude protein diet contained 1 percentage unit lower crude protein than the normal crude protein diet. Diets were formulated on a digestible amino acid basis and to be isoenergetic. Dietary corn DDGS, WM or SH lowered (P <0.01) the 7-d cumulative manure NH₃ emission and lowered (P <0.05) daily NH₃-emission rate by lowering (P <0.10) the pH of the manure but not by repartitioning nitrogen excretion from uric acid to bacterial protein. The high-fiber diets had no adverse effects (P <0.05) on egg production. The low crude protein diets did not lower NH₃ emission (P> 0.10) but caused lower (P <0.05) egg production, indicating a potential amino acid deficiency. Results of this study show that inclusion of 10% corn DDGS, 7% WM, or 5% SH in laying-hen diets is an effective means of lowering manure NH₃ emission while maintaining egg production.

Animal Nutrition