Quantitative aspects of glucose metabolism in pregnant and nonpregnant sheep

Labeled glucose was infused into four groups of ewes: nonpregnant fed; nonpregnant fasted; twin-pregnant fed; and twin-pregnant hypoglycemic and ketonemic. Mean glucose pool sizes were 157 and 127 mg/kg in nonpregnant and pregnant ewes, respectively, with decreased values in both fasting and hypoglycemia. Nonpregnant animals had glucose turnover rates averaging 4.0 g/hr (0.22 g/hr·kg 3/4 ) when fed and only 2.7 g/hr (0.15 g/hr·kg 3/4 ) after fasting. These values were only 60–80% of that of pregnant sheep, implying that glucose utilization due to twin-pregnancy was 20–40% of the total. The mean glucose space was about 27% of the body weight, indicating predominantly extracellular distribution of glucose even in hypoglycemia. In all animals about 8–10% of the exhaled CO 2 was found to be derived from glucose oxidation and about one-third of the total glucose turnover was used for CO 2 production. Comparisons of these data to values obtained from other mammals indicated further that there is a lower rate of glucose oxidation and metabolism in ruminants.