Nitrogen losses from laying hen manure in commercial high-rise layer facilities

Nitrogen (N) losses from four high-rise laying hen houses, representing fou r commercial layer farms in Iowa, were determined from measured performance data of Hy-Line W-36 White Leghorn layers (i.e., manure production, egg pr oduction, feed intake, body weight, and mortality). Nitrogen loss was 25, 3 3, 37, and 41% for Farms A, B, C, and D, respectively, based on the Total K jeldahl Nitrogen (TKN) in feed. A significant factor contributing to the di fference in the N losses was the moisture content (MC, percent on an as-is basis) in manure stored in the ventilated manure storage area of the layer houses. The higher the MC, the higher the ratio of NH3/TKNManure in the sto red manure, and therefore, the higher the percentage of N loss. Mathematica l relationships were developed. Manure handling systems played an important role in N loss by influencing MC of the manure which, in turn, affects rat e of manure decomposition. Understanding the factors affecting decompositio n and N loss mechanisms of layer manure could provide a means to significan tly reduce ammonia emissions to the atmosphere from poultry facilities.