Comparative aspects of glucose tolerance in camels, sheep, and ponies

The aim of the study was to gain informations about factors responsible for the higher level of plasma glucose in camels as compared to sheep and ponies. An intravenous glucose tolerance test was carried out with four camels, four ponies, and four sheep by infusing 1 mmol glucose per kg body weight intravenously within 3 min. Concentrations of glucose, insulin, and non-esterified fatty acids (NEFA) were estimated in venous plasma samples taken before and within 6 hr after infusion. Basal glucose values were higher in camels (7.1 +/- 0.3 mmol/l) than in ponies (4.2 +/- 0.4 mmol/l) and sheep (3.4 +/- 0.2 mmol/l). The rate of glucose elimination was markedly lower in camels (0.270 +/- 0.018 hr-1) than in sheep (0.804 +/- 0.036 hr-1) and ponies (0.858 +/- 0.084 hr-1). The insulin response after glucose infusion was more pronounced in ponies and sheep than in camels. Concentrations of NEFA in plasma dropped 30 min after the infusion in all species, however, NEFA level decreased slower in camels than in sheep and ponies. It is concluded that the markedly higher plasma concentration of glucose in camels compared to sheep and ponies may be caused by a poorer insulin response and/or a reduced tissue sensitivity to insulin.