Effect of microclimate on bacterial count and airborne emission from dairy barns on the environment

The main microclimate parameters, i.e. bacterial count and airborne emission to the immediate environment, were analyzed in a dairy barn. Air temperature, relative humidity and air flow velocity were measured on an attested Testo 400 device (Testo Inc., Germany). Air samples were collected by use of a Merck MAS-100 device (Merck KgaA, Darmstadt, Germany) onto a commercially available nutrient Columbia agar (Biolife, Milan, Italy) and incubated for 24 h in an incubator at 37 degrees C work temperature. Measurements were carried out once a week in the morning, at noon, and in the evening during October and November 2002. In the barn, measurements were performed in the animal housing area along the feedlot, and outside the barn at a distance of 5 m, 25 m and 50 m eastward and westward from the barn. The measured dairy barn temperature ranged from 11.2 degrees C to 13.1 degrees C, relative humidity from 71.3-78.6 %, and air flow velocity from 0.09-0.11 m/s. The mean value of total bacterial count in the barn air ranged from 2.82 x 10 (4) cfu/m(3) at noon to 7.76 x 10(4) cfu/m(3) in the evening. Bacterial count decreased at particular measuring sites outside the barn, with Wilcoxon matched pair test showing statistical significance (p < 0.05) at a distance of 5 m eastward and 5 m westward of the barn.