A Comparison of the effect of xylazine on plasma glucose in Hereford and Friesian steers

Abstract

Xylazine hydrochloride was administered intravenously to 17 Hereford and 17 Friesian steers on 84 occasions. In all animals plasma glucose concentration rose rapidly during the first half hour following injection. In the Friesian steers, it continued to rise steeply for a further one and a half hours, while in the Hereford steers only a small and statistically not significant further rise occurred during this time. At each sampling time from 1 to 6 hours following the xylazine injection, the glucose levels were found to be significantly different between the two breeds. It is postulated that the differing plasma glucose levels in response to xylazine between the breeds might be due to differences in the number and distribution of α2-adrenoceptors in the α- and β- cells of the pancreatic islets and in the liver. Plasma insulin concentration was considerably reduced, but no changes in the concentration of blood free fatty acids were observed.

Xylazine hydrochloride (Rompun) is widely used in domestic and wild animal species for its sedative, analgesic and muscle relaxing properties. It has been shown to produce a state of pronounced hyperglycaemia in cattle and Symods and Mallinson found that the hyperglycaemia arose from a combination of increased hepatic glucose production and reduced plasma insulin concentration. More recently it has been found that the xylazine induced hyperglycaemia is mediated via α2-adrenoceptors. The intravenous dose of xylazine to induce recumbency has previously been shown to be significantly different in Hereford steers as compared with Friesian ones. This paper reports the plasma glucose concentrations after intravenous xylazine administration in these two breeds of steer. In addition a few measurements were made on plasma insulin and free fatty acids (FFA).