Effect of glucose administration on equine fasting hyperbilirubinemia

The effects of several treatments and their routes of administration on the reduction of hyperbilirubinemia in 9 pony mares after a 3-day fast were studied. Treatments were as follows: glucose given at doses of 1.2, 2.4, and 3.7 mg/min/kg of body weight; refeeding the base-line diet; feeding straw; and IV administration of taurocholic acid at a dosage of 0.07 mumol/min/kg. The 3 glucose dosages were each given by 3 different routes: IV, intraduodenal, and intragastric. The smallest dosage of glucose given by IV route reduced the plasma bilirubin concentration only 7%, even though other measured values associated with fasting returned toward their base line; increased free fatty acid concentration was reduced by 50%; plasma insulin increased above base-line values. Except for the smallest glucose dose given by IV route, the effects of the routes of administration (IV less than intraduodenal less than intragastric) and of the doses of glucose were not significantly different. Taurocholic acid (given IV) was ineffective in reducing the plasma fasting bilirubin concentration. Refeeding the base-line diet reduced the hyperbilirubinemia by 66% in 12 hours, which was a significantly greater reduction than the effect of all other treatments except the largest dose of glucose given by intragastric route. Feeding straw was less effective than refeeding, causing only about a 30% reduction.