Akio Shiga

Stimulative effect of epinephrine on glucose production and utilization rates in sheep using a stable isotope

The rates of the production and utilization of blood glucose were measured during intravenous epinephrine infusion (2.0 nmol kg-1 min-1 for 1 hr) in sheep. An isotope dilution method with an infusion of [U-13C]glucose and nonsteady-state equations were used for the determination of blood glucose kinetics. Heart rate and concentrations of blood glucose, plasma free fatty acids, and lactate increased (P < 0.01), whereas plasma insulin concentrations tended to decrease (P < 0.06) during epinephrine infusion. The blood glucose turnover rate was 1.9 +/- 0.1 mg kg-1 min-1 before epinephrine infusion. The rate of blood glucose production increased (P < 0.01) to 6.4 +/- 0.5 mg kg-1 min-1 at 20 min after the initiation of epinephrine infusion. The blood glucose utilization rate increased (P < 0.05) gradually and reached 4.1 +/- 1.2 mg kg-1 min-1 at 60 min after the initiation of epinephrine infusion. These results suggest that in sheep, epinephrine stimulates the rates of both the production and the utilization of blood glucose and that hyperglycemia induced by epinephrine infusion is mainly due to a rapid enhancement in the rate of the production of blood glucose.

Effect of Daytime Grazing of Fresh Grass without Supplemental Feed on Serum and Milk α-Tocopherol Concentrations of Holstein Dairy Cows

Abstract Nakamura, Y., Shiga, A., Akasaka, S. and Gotoh, T. 2007. Effect of daytime grazing of fresh grass without supplemental feed on serum and milk α-tocopherol concentrations of Holstein dairy cows. J. Appl. Anim. Res., 32: 119–124. The effect of switching 5 Holstein dairy cows from concentrate-fed to roughage-fed conditions without supplemental feed for seven weeks on serum parameters and milk chemical composition in morning and afternoon milk samples was investigated. BW was not affected and blood hematocrit and total protein, glucose and triglyceride concentrations varied within normal values throughout the experiment. During day grazing period, serum non-esterified fatty acid (NEFA), milk somatic cell counts (SCC), total solids, lipids and milk and serum α-tocopherol values increased, whereas, those of milk yield, milk protein, lactose and solids-non-fat decreased. For diurnal changes, NEFA concentrations were lower, whereas, SCC, milk lipid and milk α-tocopherol concentrations were higher in the afternoon. Changes in milk chemical composition, when cows were switched from concentrate-fed to roughage-fed conditions including daytime grazing, were related to the chemical composition of the feeds consumed.