Effect of type of aviary, manure and litter handling on the emission kinetics of ammonia from layer houses

1. An experiment with laying hens of 16 to 36 weeks of age was carried out to investigate differences in ammonia emission between 3 commercially available aviary housing systems and the additional effect of manure and litter handling. 2. Ammonia emission from Tiered Wire Floor (TWF), Natura and Boleg aviary systems increased rapidly from placement of the hens to a peak at 20 weeks of age and showed respective equilibrium level at 11.55, 11.24 (N.S. compared to TWF) and 14.55 (P<0.001 compared to TWF) mg ammonia per h per hen. 3. Emission increased by 5.6% on the first day and 11% on subsequent days after removal of the manure on the belts. The litter layer increased up to about 7 cm; removal of 6.5 cm reduced emission by 20%. 4. Ammonia concentrations varied between 1 and 16 ppm, while ventilation rates were between I and 4 m(3)/h per hen to maintain inside temperature at about 22 degrees C. 5. About 82% of the droppings produced by the hens was found on the belts, either directly deposited there, or put there as litter material. The composition of the manure on the belts and the litter, a sand-droppings mixture, changed significantly during the first part of the laying cycle and differences were found between the 3 aviary systems with respect to the DM, pH, ash, N-kjeldahl and Total Ammoniacal Nitrogen concentration. 6. The changes in time and differences between the 3 systems in ammonia emissions and manure and litter composition were related to design of the systems, behaviour of the hens and degradation (of nitrogenous components) and volatilisation processes (water and ammonia).