Investigations into cardiopulmonary diseases of bovine calves
MetadataShow full item record
The purposes of study one were to determine if the successful treatment of bovine respiratory disease (BRD) in suckling calves was associated with a long-term increase in mean pulmonary arterial pressure (mPAP) and, to screen for associations between blood leukogram variables and mPAP. A cohort of Red Angus calves (n=74) were followed from birth to weaning at an altitude of 975 m. Calves were weaned at 172 ± 14 days when their mPAP was measured and whole blood collected. Thirty calves that had been treated for BRD (34 to 45 days prior) and 30 calves that had not required treatment for BRD were sampled. Treatment for BRD had no effect on mPAP (P = 0.37). Mean mPAP was 48 ± 8 mm Hg (± SD) with a minimum of 34 mm Hg and a maximum at 69 mm Hg. Weaning weight and sex tended to be associated with mPAP, but they explained just 5% of the variation in mPAP (P = 0.08; Adj. r2 = 0.05). Fibrinogen (P = 0.008) and absolute lymphocyte count (P = 0.06) were negatively associated with mPAP, whereas absolute monocyte count was positively associated with mPAP (P = 0.01). The findings of this study suggest that pre-weaning treatment for BRD does not increase a calves’ post-weaning risk of congestive right heart failure. Further, components of the immune and acute phase response system may play a role in the development and progression of pulmonary hypertension. The goal of the second study was to evaluate the effect of hypoxia on intestinal permeability and cardiopulmonary physiology in 2-month old calves. Calves were exposed to normoxic (975 m altitude; controls) or hypoxic (4,570 m altitude) conditions for 2-weeks. Pulmonary arterial pressures and intestinal permeability to mannitol and lactulose were assessed on Days 0 and 14. Calves were euthanized on Day 15. Two control calves shed occult fecal blood on Day 3; consequently, all calves were treated for coccidiosis. Control calves tended to have greater mean pulmonary arterial pressure than hypoxic calves at Day 0 (P = 0.17), but there was no difference between groups at Day 14 (P = 0.47). On average, mean pulmonary arterial pressure increased by 16 ± 2 mm Hg from Day 0 to 14 (P < 0.001). Serum lactulose was 0.8 ± 0.4 mg/L greater in the control group than the hypoxic group on Days 0 and 14 (P = 0.08). Serum mannitol was 2.0 ± 0.8 mg/L greater in control calves than hypoxic calves on Day 0 (P = 0.009) but there was no difference between groups at Day 14 (P = 0.61). In summary, hypoxia did not affect intestinal permeability, but the results were confounded by intestinal disease. Interestingly, the two calves that had bloody scours had the greatest pulmonary arterial pressures and diffuse alveolar damage. The findings of this study provide preliminary evidence that intestinal disease may contribute to the development of pulmonary diseases in cattle.