Glucose and xylitol tolerance tests for ketotic and healthy dairy cows.

Intravenous administration of 500 ml of 50% glucose solution to 10 nonketotic dairy cows increased the blood glucose and insulin concentrations 7-fold immediately following administration. Blood glucose and insulin concentrations of ketotic cows were about 6- and 3-fold higher, respectively, immediately following glucose administration. Administration of 1000 ml of 25% xylitol (xylo-pentane-1,2,3,4,5-pentol) in nonketotic cows increased blood glucose and insulin concentrations 2- and 9-fold, respectively. Ketotic cows treated with xylitol exhibited blood insulin concentration 12-fold higher following administration. This insulin increase might be explained by a decrease in insulin degradation because of the diffusion of xylitol, which is not dependent on insulin in peripheral tissues. For ketotic cows given xylitol, serum concentrations of free fatty acid decreased, and triglyceride concentrations and aspartic acid aminotransferase activity increased, but values were unchanged by xylitol administration to nonketotic cows. Thus, for ketotic cows, the responses of the blood glucose and insulin concentrations to xylitol administration were better than those responses to glucose administration. Improvements in clinical signs, i.e., disappearance of urinary ketone bodies and recovery to normal feed consumption, also suggested the usefulness of xylitol administration for the treatment of ketosis.