Comparison of the odour impact of cattle housing with and without an outdoor exercise area

Outdoor exercise areas in loose cattle housing systems represent close-to-the-ground emission sources. Previously, outdoor exercise areas were not taken into account when calculating the minimum distance to residential zones. The aim of these studies was to highlight any possible effect of outdoor exercise areas with solid flooring on odour impact. For this, the odour impact of a 100 m2 outdoor exercise area exposed to a free flow of air was determined by means of an experimental approach. In addition, the odour impact of ten loose dairy-cattle housing systems with an animal population of between 12 and 44 livestock units was recorded. The emitting areas comprised 100 to 600 m2, between 50 and 180 m2 of which formed part of the outdoor exercise area. Odour impact was determined via odour-plume inspections with assessors. After the first inspection rounds with a soiled outdoor exercise area, the surface of the outdoor exercise area was covered with sheeting. Further inspections then followed according to the situation where no outdoor exercise area was used. The impact-side odour intensity was explained by means of a linear mixed-effects model. In this context, the variables ‘distance to source’ and ‘wind speed’ were significant for the test area, while ‘surface area’ was an additional variable for the farms. The results highlight the odour relevance of outdoor exercise areas. Incorporating this odour-relevant area into the distance recommendations is therefore essential in order to prevent odour complaints.