Effects of Supplemental Energy as Starch on Tissue Responsiveness and Sensitivity to Insulin in Goats

Abstract

Intact adult male goats were fed diets at 1.0, 1.5 and 2.0 times the metabolizable energy for maintenance, each for 21 days. Supplemental energy above maintenance was supplied as corn starch. Tissue responsiveness and sensitivity to insulin were evaluated using a hyperinsulinemic euglycemic clamp technique with four levels of insulin infusion. The concentrations of plasma metabolites and insulin were also measured at 6h after feeding. At 6h after feeding, plasma total amino-nitrogen, acetate and propionate concentrations were increased (P<0.05) with increasing energy intake, but plasma insulin concentration was unchanged. In the clamp experiment, basal blood glucose and plasma insulin concentrations were unaffected by energy intake. Maximal glucose infusion rate (tissue responsiveness to insulin) increased (P<0.05) with increasing energy intake, but the plasma insulin concentration at half-maximal glucose infusion rate (insulin sensitivity) was unaffected by energy intake. These results suggest that in adult male goats energy supplementation with starch enhances tissue responsiveness to insulin, but has no effect on insulin sensitivity as determined by the glucose clamp approach.