Characters of airborne contaminants emission from half stair-step cage breeding hen house during winter daytime

Abstract: Environment and disease problems have negative effects on the development of egg industry. Airborne particles, airborne microorganisms and ammonia are the main contaminants emitted from laying hen houses. These air contaminants emitted from animal buildings may harm the environment and public health. PM2.5 can deposit in human lung, causing respiratory responses. It increases the risk of Asthma, vascular inflammation, lung cancer and heart disease. Airborne microorganisms with airborne particles as the carrier can cause cross disease infection of birds, threatening the biosecurity of the farm. Ammonia may harm the health of workers and birds, and reduce the animal production performance. In this research, the emission of airborne particles, airborne microorganisms and ammonia from a breeding hen house were monitored in the winter daytime in Beijing, China. Approximate 14,000 layer breeding hens (32 week-old at the start of the experiment) and 400 adult male chickens were confined in 3 stair-step cages in the tunnel-ventilated house. During the experiment, fresh air was pulled in through 38 air inlets, evenly distributed along the sidewalls, and only one of the six exhaust fans (the experimental fan) was operated intermittently on a thermostat to control indoor air temperature. A new sampling system for airborne particles, airborne microorganisms and ammonia was designed, respectively. The airborne particles sampling system consists of a PVC sampling manifold, a glass fiber membrane, a drying tube, a flow meter and a vacuum pump. The ammonia sampling system consists of a PVC sampling manifold, an air washing bottle with boric acid solution, a drying tube, a flow meter and a vacuum pump. The airborne microorganisms sampling system consists of a PVC sampling manifold, an airborne microorganism sampler and a vacuum pump. The study was carried out in the winter daytime using these sampling systems. Average airborne particle and ammonia concentrations at the outlet sampling location were measured from 8:00—18:00 on each sampling day. Airborne microorganism concentration was sampled at the outlet location on each sampling day. Starting time were 8:00 and 13:00 (twice, 30 min for each time). In the experiment period, the temperature and humidity inside and outside the laying hen house were tested and recorded. Ventilation rate was calculated by the static pressure difference and the fan performance curve supplied by the manufacturer. The results showed that:1) In the winter, the breeding hen house in Beijing conducted intermittent ventilation. The ventilation rate per hen and the ambient temperature showed positive correlation (P<0.05, R2=0.8837). 2) The air temperature in the laying hen house in the winter was controlled between 18.0 and 20.0 ºC. In the experiment period, the emission concentration of airborne particles was between 0.5 and 0.8 mg/m3, averaging 0.7±0.1 mg/m3. The emission rate was between 1.0 and 1.5 mg/h per hen, averaging 1.2±0.2 mg/h. The emission concentration of airborne microorganism was between 4.0 and 4.5 log10 CFU/m³, averaging 4.2±0.1 log10 CFU/m³. The emission rate was between 4.3 and 4.8 log10 CFU/h per hen, averaging 4.5±0.1 log10 CFU/h. The emission concentration of ammonia was between 7.6 and 14.3 mg/m3, averaging 10.8±2.3 mg/m3. The emission rate was between 8.1 and 13.7 mg/h per hen, averaging 11.1±1.9 mg/h. Ammonia emission rate of this house was higher than that of layer hen houses with manure belt, but lower than that of high rise layer hen houses. In the experiment period, the ambient temperature was lower than indoor temperature. The ambient temperature and the ventilation rate showed small fluctuation. No correlativity was found between air contaminants emission concentration, emission rate and ambient temperature, ventilation rate, and indoor relative humidity. The results provided basic data and theoretical basis for the air contaminants emission from layer hen houses in China.