Both metabolic rate and pulmonary ventilation change throughout 24h with a circadian pattern. Because their changes occur almost in synchrony and by a similar amount, blood gases may remain steady within a narrow range. We tested this possibility in five cows (Bos taurus, Bruna Italiana breed), maintained in a stable at 29°C, under natural light-dark (LD) regime, by measuring arterial blood gases every 3h for 2 days. All cows presented a clear day/night pattern of body temperature (Tb), with an average peak-trough difference (PTD) of 0.5°C. Breathing rate oscillated significantly in three out of five animals, with a group-mean PTD of 2 breaths per minute, and it was time-advanced with respect to the oscillation of Tb. Significant oscillations in arterial pH, bicarbonate, partial pressure of oxygen and partial pressure of carbon dioxide (PaCO2) were observed in, respectively, 1 cow out of 5, 1/5, 3/5 and 5/5. Of all these variables, group-mean analysis revealed a significant day/night pattern only for PaCO2, and even in this case the average PTD was less than 1mmHg. We conclude that, in the cow, blood gases remain remarkably stable throughout the 24h. Hence, the daily oscillations of body temperature, breathing rate, and probably of many other factors affecting metabolic rate and pulmonary ventilation do not preclude an excellent homeostasis of blood gases.

DAY/NIGHT PATTERN OF ARTERIAL BLOOD GASES IN THE COW

PICCIONE, Giuseppe;CAOLA, Giovanni;
2004

Abstract

Both metabolic rate and pulmonary ventilation change throughout 24h with a circadian pattern. Because their changes occur almost in synchrony and by a similar amount, blood gases may remain steady within a narrow range. We tested this possibility in five cows (Bos taurus, Bruna Italiana breed), maintained in a stable at 29°C, under natural light-dark (LD) regime, by measuring arterial blood gases every 3h for 2 days. All cows presented a clear day/night pattern of body temperature (Tb), with an average peak-trough difference (PTD) of 0.5°C. Breathing rate oscillated significantly in three out of five animals, with a group-mean PTD of 2 breaths per minute, and it was time-advanced with respect to the oscillation of Tb. Significant oscillations in arterial pH, bicarbonate, partial pressure of oxygen and partial pressure of carbon dioxide (PaCO2) were observed in, respectively, 1 cow out of 5, 1/5, 3/5 and 5/5. Of all these variables, group-mean analysis revealed a significant day/night pattern only for PaCO2, and even in this case the average PTD was less than 1mmHg. We conclude that, in the cow, blood gases remain remarkably stable throughout the 24h. Hence, the daily oscillations of body temperature, breathing rate, and probably of many other factors affecting metabolic rate and pulmonary ventilation do not preclude an excellent homeostasis of blood gases.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11570/1582982
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