The effect of feeding on cerebral blood flow and oxygen consumption in the new‐born calf

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Abstract
The effect of feeding on cerebral blood flow and O2 consumption was investigated in unrestrained calves from 7-28 days after birth. Cerebral blood flow was determined using an inert gas clearance technique, and O2 consumption by the simultaneous measurement of the arterio-cerebral venous O2 content difference. Cerebral blood flow increased during feeding from 74 .+-. 4 to 116 .+-. 9 ml/100 g per min and reverted afterwards to the pre-feed level. No alteration in cerebral O2 consumption occurred. Feeding was associated with an increase in mean arterial blood pressure and heart rate, and mild asphyxia. The sensitivity of the cerebral circulation to alterations in arterial CO2 pressure [PaCO2] was investigated in 7 calves under sodium pentobarbitone anesthesia. In the range of PaCO2 15-75 mm Hg the relationship was linear (r [correlation coefficient] = 0.71; P < 0.001) with an average slope of 0.68 ml/100 g per min mm Hg per PaCO2. Increases in mean arterial blood pressure comparable to those occurring during feeding (96 .+-. 6 to 159 .+-. 8 mm Hg) were produced by compression of the thoracic aorta in 3 calves under sodium pentobarbitone anesthesia and were associated with an increase in cerebral blood flow from 48 .+-. 4 to 76 .+-. 8 ml/100 g per min. No significant change in calculated cerebral vascular resistance occurred during either feeding or aortic compression. The rise in blood pressure which occurs during feeding in the calf evidently exceeds the autoregulatory capacity of the cerebral circulation.