Some metabolic effects of cold stress on undernourished non-pregnant ewes

Abstract

Four very fat and four moderately fat ewes were undernourished for 33 days, during which time the mean decrement of body weight was 8%. The sheep were then shorn and two each of the fat and moderately fat sheep were exposed to an air temperature of 3°C while the others remained at 21 ± 5°C. The same limited quantity of food was offered at both temperatures.

Three out of the four cold ewes died, whereas none of the ewes at 21°C died. The moderately fat cold ewes died within 110 hr. They showed marked protein catabolism for 24–48 hr prior to death and rapid losses in body weight accompanied by large losses in body water, urinary nitrogen, creatine, and potassium. Both animals contained substantial amounts of fat at death. One of the fat ewes died on the 10th day of cold, showing an increase in urinary nitrogen but no elevation of uninary volwne or urinary potassium. The other cold, undernourished fat ewe survived after showing increased protein catabolism during the first 10 days of cold.

Transaminase activity was elevated in all cold-stressed ewes; lysosomal hydrolase activity was elevated in the circulation of animals in the cold, especially in the fat ewe that died.

These results suggest that previous undernutrition alters the response of sheep to a cold stress and that a cold stress and a degree of undernutrition, each alone readily tolerated by the sheep, may together prove fatal.