THE INFLUENCE OF CORTISOL ON FOOD INTAKE AND GLUCOSE METABOLISM IN SHEEP

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Abstract
SUMMARY: Some metabolic effects of cortisol were investigated in non-pregnant ewes fed either ad lib. or on a restricted ration. Cortisol (25 mg./day) administered for a period of 21 days stimulated the voluntary food intake of fat ewes offered food ad lib. Higher levels of cortisol (50 and 75 mg./day) administered for similar periods subsequently had little additional effect on voluntary food intake, but an even greater cortisol dose (150 mg./day) resulted in a marked decline in voluntary food intake. Ewes fed a constant restricted ration did not refuse food at any time during cortisol administration. Urinary nitrogen excretion was increased during cortisol administration but sequential increases in the cortisol dose failed to increase urinary nitrogen excretion proportionately above the level attained during administration of 25 mg. cortisol/day. The blood glucose level was elevated progressively as the level of cortisol administered was increased. Similarly, tolerance for a glucose load was impaired progressively. Only very small changes in blood ketones and plasma free fatty acid levels were observed during cortisol administration. The changes in blood glucose during cortisol administration cannot be accounted for by changes in gluconeogenesis, and it is suggested that they reflect a progressive impairment of glucose utilization relative to the blood glucose level, though not a reduction in total glucose utilization.