PATHOPHYSIOLOGIC STUDIES OF INFECTIOUS BOVINE-RHINOTRACHEITIS IN HOLSTEIN-FRIESIAN CALF

  • 1 January 1978
    • journal article
    • research article
    • Vol. 39  (5) , 779-783
Abstract
Pulmonary function changes in 6 Holstein-Friesian calves, 4 to 8 wk of age, were studied for 10 to 11 days following experimental inoculation with infectious bovine rhinotracheitis (IBR) virus. Calves had no demonstrable antibody titer against IBR virus before inoculation, and all calves responded to the virus by postinoculation day 3 with high fever (> 40.6.degree. C) and rapid, shallow breathing. Analysis of blood gases demonstrated a progressive rise in Pa[partial arterial pressure]CO2 but no change in PaO2. Acid-base state remained normal. Tidal volume decreased with time; conversely, minute ventilation, functional residual capacity, O2 consumption and CO2 production increased. Alveolar ventilation failed to increase as much as predicted. Studies of respiratory mechanics showed a progressive increase in total pulmonary resistance but without change in dynamic pulmonary compliance. A steady-state N2 washout test was used with these calves, and results suggested impairment of intrapulmonary gas mixing as the disease progressed. Microbiologic, pathologic and histopathologic analyses were consistent with the picture of acute IBR. This study demonstrated the ability to measure pulmonary function changes in nonanesthetized large animals suffering from respiratory tract disease. The pathophysiologic features of acute IBR infection was characterized in the bovine species as an obstructive lung disease resulting in increased resistance to breathing, retention of CO2 and increased resting lung volume.