Effect of somatic growth on pulmonary function values in healthy Friesian cattle.

Growth-related changes in pulmonary function values (PFV) of cattle were investigated by a cross-sectional study of 40 healthy Dutch Friesian cattle, 3 days to 13 years of age and weighing 37 to 660 kg. Technical and methodologic procedures and body conformation and condition were standardized. A regression analysis was done with 4 independent variables (body weight, thoracic perimeter, body surface area, and age) and with PFV measured in this study. Ventilation values, dynamic lung compliance, and viscous work of breathing changed linearly with somatic growth. Respiratory frequency, total pulmonary resistance, and arterial oxygen tension showed an exponential relationship with all the independent variables. On the other hand, intrapleural pressure values were weakly correlated with body size indexes. The most important growth-related changes in PFV occurred at approximately 1 year of age. A significant (P less than or equal to 0.05) difference between immature and mature cattle was shown for the blood-gas values and the specific values of the breathing mechanics. The dynamic lung compliance/lung weight was lower and the total pulmonary resistance X minute volume was higher in cattle than in other domestic mammals. The regression equation, giving the best fit of the data, was selected for each PFV.