Effect of Intrajugular Administration of Insulin on Feed Intake, Plasma Glucose and Plasma Insulin of Sheep

Abstract

The effect of intrajugular administration of insulin on feed intake, plasma glucose and plasma insulin of 16 wether sheep was studied. A concentrate ration was fed ad libitum to eight wethers, and a forage ration fed to eight different wethers. For each ration, feed intake of four of the eight wethers was measured in one experiment and blood was sampled from the other four wethers at 15, 30, 60 and 120 minutes after injection in a second experiment. The four treatments were saline, 1 mU, 6 mU and 2,000 mU insulin/kg body weight. The highest insulin dose did not affect feed intake of either ration despite producing a marked hypoglycemia, whereas the 6 mU insulin treatment depressed feed intake 1 hour after injection with small changes in concentration of plasma glucose in sheep fed either the concentrate or forage ration. Concentration of plasma insulin was elevated 15 minutes following the 6 mU insulin treatment for the concentrate and forage ration, while 1 mU insulin did not affect plasma insulin. The results of this study suggest a possible role for insulin in the short-term control of feeding in sheep fed either a concentrate or forage ration.