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.
