Studies on the carbohydrate metabolism of sheep. XV. The adrenal response to the climatic stresses of cold, wind, and rain

Abstract

Plasma cortisol values were consistently elevated in undernourished pregnant ewes carrying a 7–10 months' fleece during 24–48 hr periods of climatic stress involving cold (2–3°C), moderate wind, and discontinuous or continuous heavy "rain". Increases in plasma cortisol were delayed, compared with the prompt response which occurs during emotional stress. Cold alone had no detectable effect; very high levels of plasma cortisol comparable with those often encountered during short periods of emotional stress were recorded only during periods of continuous "rain" of an intensity rarely, if ever, encountered in practice. Increases in blood glucose level during stress were considerably less in pregnant than in non-pregnant ewes; this is considered to reflect high foetal uptake of glucose. Overall, the stress was antiketogenic, probably owing to the ketolytic effect of increased blood glucose. In the latter part of the stress period, however, when plasma cortisol values were high, blood ketone levels increased in spite of elevated blood glucose; this ketogenic effect of stress is considered to be mediated by the adrenal cortex. The results are discussed in relation to current theories on the pathogenesis of ovine pregnancy toxaemia.