Ammonia emission and nutrient load in outdoor runs of laying hens

Ammonia emission and nutrient load in outdoor runs of laying hens were measured at a commercial farm with an outdoor run for 3000 hens, and at an experimental farm with two outdoor runs, each for approximately 250 hens. Ammonia emission was recorded at 5, 10, 15 and 20 m from the hen house, using the ventilated chamber technique. Nutrient load was determined by analysing the fresh droppings. The results show ammonia emission to decrease with increasing distance from the hen house. The average emission per hen was 2.0 mg h−1 for the run of the commercial farm, and 0.95 and 0.86 mg h−1 for the two runs of the experimental farm. The nutrient load within 20 m from the hen house exceeded the threshold value for nutrient supply from manure (170 kg N and 44 kg P per ha] by a factor 15 on both the commercial farm and the experimental farm. The results show that the ammonia emission from the outdoor run of laying hens was relatively small compared with the emission from the hen house and that the nutrient load in the outdoor run near the house by far exceeded maximum acceptable levels.