THE EFFECT OF ALPHA(2)-ADRENOCEPTOR STIMULATION WITH GUANFACIN ON HEAT-PRODUCTION OF RESTRICTED FED STEERS KEPT AT -9-DEGREES-C 11-DEGREES-C OR 28-DEGREES-C AND ON AD-LIBITUM FED STEERS ACCLIMATED TO -19-DEGREES-C AND 22-DEGREES-C

1. Guanfacin, an alpha(2)-adrenergic agonist was used to examine the a lpha(2)-adrenoceptor mediated thermogenic and metabolic effects in ste ers (Bos taurus) kept at either -9, 11 or 28 degrees C and in ad libit um fed steers acclimated to -19 and 22 degrees C. 2. Guanfacin reduced (P < 0.05) the heat production in steers kept in the -9 degrees C and 11 degrees C thermal environments by 23 and 20% respectively. At 28 d egrees C thermal environment the reduction (P < 0.1) in heat productio n was only 8%. 3. The rectal temperature was lower (P < 0.05) at -9 de grees C, unchanged at 11 but elevated (P < 0.05) at 28 degrees C in re sponse to guanfacin. 4. Guanfacin reduced (P < 0.05) the heat producti on in ad libitum fed steers by 12%. 5. In conclusion, cattle may have the potential to improve energy conservation by activating alpha(2)-ad renoceptor-mediated processes in response to thermal and nutritional s timuli. In addition, guanfacin may reduce maintenance energ)y requirem ents of steers by 12-20%.