AEROSOL GENERATION AND REMOVAL MECHANISMS IN AN ENCLOSED CALF BARN

The mortality rate of neonatal calves raised in the northeastern United States commonly exceeds 20 percent in enclosed barns. Infectious diarrhea and pneumonia are the diseases responsible for limiting the production potential of the calves, causing death in severe cases. One probable means of infection of the calf is inhalation of respirable aerosol with attached pathogens that deposit in the lower respiratory system. Respirable aerosol for a calf is predominantly between 0.5 and 2.0 (mu)m in diameter. To limit the spread of disease, alterations of the calf barn environment are necessary. The purpose of this thesis is to quantify the aerosol generation mechanisms and review aerosol removal mechanisms in an enclosed calf barn to present recommendations for improving the growth environment of the calf.;Respirable aerosol generated by calves and humans was insignificant compared to aerosol concentrations naturally occurring in a dairy farm environment. Viable aerosols were generated by calves via three mechanisms; defecation, urination, and coughing. Ventilation rates necessary to control the viable aerosol concentration are too high to conserve energy in the barn. Supplemental air cleaners are recommended for aerosol removal. Future research should quantify the concentration of viable aerosols that cause respiratory infection in calves so that ventilation and air cleaner flow rates may be specified.;A clean room isolated from surrounding sources of respirable aerosol was constructed to monitor the aerosol generation by a single calf contained on an elevated stall. The concentrations of respirable aerosols generated within this room was measured using a particle counter. Viable aerosols containing microorganisms were measured using an Andersen Sampler. Aerosol production from generation mechanisms of the calf were quantified, including defecation, urination, body movements, and coughing. Human aerosol generation by walking and jumping was also studied. Naturally occurring concentrations of respirable aerosol were determined through sampling the dairy farm environment. Aerosol generation data was used to construct a simulation model of the aerosol concentration in a calf barn. The model evaluated ventilation rates, supplemental air cleaners, and air mixing factors for aerosol reduction.