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The effect of the α2-adrenergic agonist, guanfacin, on the energy metabolism of steers fed on low-quality-roughage diets

Published online by Cambridge University Press:  09 March 2007

R. A. Hunter
R. A. Hunter
Affiliation:
CSIRO Division of Tropical Animal Production, PO Box 5545, Rockhampton Mail Centre, Queensland 4702, Australia
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Abstract

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The effect of the α2-adrenergic agonist, guanfacin, on the energy metabolism, feed intake and live weight (LW) change of steers was studied in three experiments. In the first, the metabolic rate of twelve steers was measured after a 72 h fast. The next day, after a 96 h fast, six steers were injected intramuscularly with 15 mg guanfacin in sterile saline (9 g sodium chloride/l) and six with sterile saline alone, and metabolic rate was measured again. Treatment significantly (P < 0.01) lowered metabolic rate by approximately 20% (53.9 v. 66.8 kJ/kg per d). In the second experiment twelve steers were fed on long-chopped, low-quality roughage (Pangola grass (Digitaria decumbens) hay) ad lib. for 6 weeks. Six steers were continuously infused through a jugular catheter with 15 mg guanfacin/d (about 40 μg/kg LW) in sterile saline. The other six served as controls. There was no significant effect of treatment on feed intake (g dry matter (DM)/kg LW) or the rate of LW loss. Treatment significantly (P < 0.05) increased the retention time of fluid (17.9 v. 22.1 h) in the alimentary tract. In the final experiment twenty-three steers were divided into four treatment groups and fed on long-chopped, low-quality roughage (Pangola hay). Treated animals were continuously infused with guanfacin at the rate of 20, 40 or 80 μg/kg LW per d. Control steers were not infused. At the end of the 6-week feeding period metabolic rate was measured after a 72 h fast. Regardless of dose, guanfacin significantly (P < 0.01) lowered metabolic rate. Feed intake was not significantly affected by treatment but the rate of LW loss was significantly (P < 0.05) less in treated steers.

Keywords

Guanfacinα2-Adrenergic agonistEnergy metabolismLow-quality-roughage dietsSteers
Type
Energy Metabolism
Information
British Journal of Nutrition , Volume 67 , Issue 3 , May 1992 , pp. 337 - 343
Copyright
Copyright © The Nutrition Society 1992

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