Control of gluconeogenesis in the lactating sheep.

Ewes which had been lactating for 3--4 weeks and which had been milked by hand from the day of parturition were subjected to food restriction for 4 days. One group of three ewes was fed ad libitum and a second group of four ewes was fed to meet calculated requirements for maintenance and milk production. Over 4 days food intake was reduced by 80% in both groups of ewes. In response to food restriction, milk yields and body weight decreased. Blood amino acids, plasma glucose, glucose pool size, glucose irreversible loss, insulin, thyroxine and the insulin: glucagon molar ratio decreased. In contrast, plasma glucagon remained relatively unaffected and plasma free fatty acids and growth hormone increased. These changes were similar for both groups of ewes and were reversed when food intake was restored. The results suggest that the hormonal control of gluconeogenesis in the ruminant is similar to that in the non-ruminant.