PHYSIOLOGICAL AND PATHOPHYSIOLOGICAL ASPECTS OF RESPIRATORY-FUNCTION IN THE BOVINE SPECIES

Anatomical and functional characteristics of the respiratory system of the bovine can explain the greater susceptibility of cattle to respir atory disease compared with other species. As the pulmonary function o f calves does not reach maturity before developing a body weight of 30 0 kg they are more susceptible to respiratory problems than adults. In the pathogenesis of respiratory disease in calves, disturbances in ve ntilation, pulmonary diffusion, pulmonary haemodynamics and/or a ventr ilation-perfusion mismatching may play important roles in resulting in decreased arterial O-2 levels. An increasing partial pressure of CO2 as is often observed in ventilatory disturbances or in a disturbed ven tilatory distribution, causes respiratory acidosis. Because of the com pensatory mechanisms of the respiratory and circulatory systems, an ad equate total oxygen uptake can be maintained despite respiratory insuf ficiency until shortly before death. However, during stress of exercis e, such as through transportation, these compensatory mechanisms may b e impaired.