[Microbial contamination of the air in the housing of laying hens]

Studied were buildings of one and the same design, sizing 92/12/3.5 m. Building A of mechanical ventilation through negative pressure housed 9,000 layers of the White Leghorn breed, and building B of ventilation with equated pressure, providing the same debit per kg biomass, housed 20,000 layers. The air in the buildings, in the close surrounding as well as the feed and soil were investigated with regard to the total counts of organisms as cultured in meat and peptone agar and with regard to the individual counts of coli bacteria, microscopic fungi and hemolytic cocci, and Salmonellae. It was found that the microbial contamination of air on the productional premises and of atmospheric air closely surrounding the buildings, was higher in building A. There were differences in the microflora of the air at the level of the individual stories in building B. The differences in the microbial contamination of air between the two buildings was the result of reconstructions concerning the ventilation system as well as of making it more effective.