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High-altitude exposure is physiologically challenging. This is particularly true for animals native to low-altitude environments, such as British breeds of cattle. The objective of this study was to document the effect of high altitude on select physiological parameters of healthy beef calves (Bos taurus) born and raised on a high-altitude ranch typical of the Rocky Mountain region. Pulmonary arterial pressures, arterial blood-gas tensions, serum biochemistry, and hematocrit were evaluated. The calves studied were a composite of British (50%-75%) and Continental (25%-50%) breeds born on one ranch at an altitude of 2410 m. Calves were sampled at an altitude of 2410 m when 1 month old and again at an altitude of 2730 m when 3 and 6 months old. Between 3 and 6 months of age, calves had access to grazing from 2730 m to approximately 3500 m above sea level. On each occasion, 16 to 50 calves were sampled. Only calves that remained healthy throughout all three testing periods were included in the dataset. Calves with the highest pulmonary arterial pressures at 1 month of age tended to have the highest pressures at 6 months of age (r = 0.43, P = 0.16, n = 12). Respiratory alkalosis was greatest at 6 months of age (pH 7.48 ± 0.06). Mean alveolar-arterial oxygen pressure gradients were 11.7 and 11.6 mmHg at 3 and 6 months of age, indicating poor transfer of oxygen from the alveoli into the pulmonary blood. Median values for blood lactate ranged from 1.4 to 3.4 mmol/L indicat- ing substantial anaerobic respiration at all ages. Mean hematocrits were # 35.7%, only slightly higher than values obtained from age-matched calves at sea level. These results suggest that the provision of oxygen to the peripheral tissues of beef calves may be compromised at altitudes over 2410 m. This may have implications for diseases of the cardiopulmonary system.

Pulmonary arterial pressures, arterial blood-gas tensions, and serum biochemistry of beef calves born and raised at high altitude