GLUCOSE AND ALANINE METABOLISM IN CHRONICALLY COLD-EXPOSED SHEEP

Abstract

Glucose and alanine metabolic interrelationships (measured with 3H-glucose and 14C-alanine) were examined in closely shorn wethers subjected to thermoneutral (TN) temperatures or chronic cold exposure (CE, < 21 d). Three treatments (n = 5–6 per treatment) were used: (1) fed to maintain weight at 18–20 °C (TN-Low); (2) fed to maintain weight at 0–4 °C (1.5 × TN-Low intake, CE-Hi); and (3) fed at CE-Hi intake at 18–20 °C (TN-Hi) to distinguish effects of the higher feed intake in the CE-Hi sheep from the cold per se. Plasma glucose pool size increased (P < 0.1) in CE-Hi sheep from 1.81 (TN-Low) and 1.83 (TN-Hi) to 2.40 mmol kg−0.75. Plasma glucose entry rates increased (P < 0.001) from 0.91 (TN-Low) to 1.29 (TN-Hi) to 1.78 (CE-Hi) mmol h−1 kg−0.75. Plasma alanine entry rates showed a tendency (P = 0.19) to increase in the CE-Hi sheep. Percentage alanine converted to glucose increased (P < 0.1) from 14.2% (TN-Low) and 13.4% (TN-Hi) to 21.5% (CE-Hi). These results indicate that increased glucose metabolism in cold-exposed sheep is a chronic adaptation. The data also suggest that the rate of alanine conversion to glucose increases during chronic cold exposure. Key words: Alanine, glucose, chronic cold exposure, sheep