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To investigate the characteristics of plantain (PL), a forage herb, as a feed for ruminants, chemical components, energy digestibility, rumen constituents, concentrations of blood metabolites (glucose, nonesterified fatty acids, lactate, acetate, and propionate), and insulin were measured in four sheep fed PL and orchard grass (OR), a forage. Net blood glucose turnover rate in response to cold exposure (0-4°C on Day 5) was also determined using an isotope dilution method of [U-13 C]glucose. Dry matter intake was numerically lower for the PL diet than for the OR diet (942 versus 1154 g day -1 ), and was lower (P = 0.03) during cold exposure than in the thermoneutral environment (1009 versus 1087 g day -1 ). Energy digestibility was similar between the PL and OR diets. No significant differences in blood metabolite and insulin concentrations in plasma were detected between the PL and OR diets. Net blood glucose turnover rate was also similar between the diets. The rate increased (P = 0.002) during cold exposure, with no significant diet and environment interaction. The forage herb PL seems to be comparable to OR as regards digestive and metabolic characteristics and blood glucose metabolism of sheep.

An isotope dilution method using [U-(13)C] glucose infusion and a glucose clamp approach were applied to determine the effects of supplemental Cr and cold exposure on blood glucose turnover rate and tissue responsiveness and sensitivity to insulin in eight sheep. The daily profiles of blood metabolites and hormones were also determined. The sheep consumed diets containing either 0 or 1 mg of Cr/kg from a high-Cr yeast and were exposed from a thermoneutral environment (20 degrees C) to a cold environment (0 to 4 degrees C) for 9 d. The experiment used a crossover design. Body weight was lost (P = 0.02) during cold exposure, regardless of Cr supplementation. Blood glucose turnover rate and the maximal glucose infusion rate did not differ between diets, but both were higher (P = 0.0004 and P = 0.0001, respectively) during cold exposure than in the thermoneutral environment. The plasma insulin concentration at half-maximal glucose infusion rate changed with neither diet nor environment. Plasma concentrations of glucose and NEFA increased (P < 0.05) during cold exposure for both diets. In sheep, Cr supplementation, 1 mg/kg of diet as high-Cr yeast, has little influence on blood glucose metabolism and insulin action, whereas cold exposure enhances both without further modification by Cr supplementation.

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, 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 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.

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