Ovine ketosis. VI. The effect of starvation on the blood levels of ketones and glucose in pregnant ewes from Karoo and the Highveld regions of South Africa

Abstract

The blood levels of glucose and ketones during fasting were determined in two groups of young preparturient ewes from the Karoo region of South Africa where pregnancy disease is endemic, and from the Highveld region where this metabolic disorder rarely occurs among sheep. During the fast, clinical symptoms of pregnancy disease were observed in six out of 12 Karoo ewes but in none of the High veld ewes; the Karoo ewes lost only two-thirds of the weight lost by the Highveld ewes despite the similarity of the starting weights of both groups; the Karoo ewes had higher blood glucose and lower blood ketone levels than the Highveld ewes; in both groups of animals fasting changed the order of magnitude of the individual ketone bodies from beta-hydroxybutyric acid > acetoacetic acid > acetone to acetone > beta-hydroxybutyric acid > acetoacetic acid. The effect of feeding green lucerne in place of lucerne hay in the prefasting diet was to raise the fasting blood glucose levels, to lower the rate of increase in the fasting blood ketone levels, and to reduce greatly the incidence and intensity of the clinical symptoms. The findings clearly indicated that the susceptibility to pregnancy disease of animals subjected to exactly the same experimental treatment, after having been kept under identical conditions for six months immediately prior to experimentation, depended on their condition prior to this time. The possibility that the symptoms of cerebral dysfunction were due to impaired glucose metabolism often associated with Karoo sheep rather than to the hypoglycaemia per se is discussed.