Litter Composition and Ammonia Emission in Aviary Houses for Laying Hens. Part 1: Performance of a Litter Drying System

Abstract

Abstract The effects of a litter drying system are reported on the composition of the litter and the emission of ammonia from a tiered wire floor aviary housing system for laying hens. Air velocities above the litter, a mixture of droppings and sand, were increased by means of air that was sucked from the top of the room and blown through holes in ducts at floor level. The dry matter content of the litter was higher (above 900 g/kg) and the total ammoniacal nitrogen (0·7 g/kg) and pH (7·3) of the litter were remarkably lower than in aviaries without forced drying of litter (dry matter 750–850 g/kg, total ammoniacal nitrogen 2–3 g/kg, pH about 8·6). Concentrations of ammonia in the exhaust air were below 5 p.p.m. and the emission of ammonia from the house reached a stable emission level of about 2·0 mg/h per hen when hens were about 30 weeks old. This emission was caused by the litter and the manure on the belts, and was reached when manure on the belts was removed daily and about 500 m 3 /h of air were blown evenly over the litter by means of three ducts. The litter drying system effectively maintained the dry matter content of the litter at a high level and minimized the degradation of nitrogenous components into ammonia. A possible increase of the volatilization rate of ammonia because of higher air velocities was of minor importance.