Effect of insulin and tolbutamide on growth rate, blood glucose and body composition of lambs.

Twenty-four 8 to 9-week old lambs were used in each of two experiments. They were fed ad libitum a pelleted ration containing 30% hay and 70% concentrates. Blood glucose was determined on half of the lambs in each experiment every second week at 0, 4, 8 and 24 hrs after treating with insulin or tolbutamide. In the first experiment, protamine zinc insulin given subcutaneously every second day at levels of 0.2 and 1.0 I.U./kg of body weight, had no significant effect on blood glucose level, growth rate or carcass composition. In the second experiment, tolbutamide and insulin were given to different groups of weanling lambs with the dosage increased every 2 weeks until signs of hypoglycemia began to appear. The dosage was then kept at this level until the lambs reached market weight. A significant decrease in blood glucose was observed in both groups of lambs at six weeks when the dosage of tolbutamide reached 120 mg/kg and the insulin reached 40 I.U./kg. Lassitude and anorexia were observed in one lamb receiving insulin. Neither treatment significantly affected growth rate or carcass composition. It was concluded that supplemental insulin or tolbutamide are of no value in fattening lambs.