DEXMEDETOMIDINE VS. XYLAZINE: EFFECTS ON BEHAVIOUR AND PLASMA CONCENTRATIONS OF CORTISOL AND SUBSTANCE P IN CALVES UNDERGOING TRUE AND SHAM DISBUDDING

Summary Disbudding is a routine painful procedures carried out on cattle to facilitate management (Gottardo et al. 2011, Duffield 2008, Laine et al. 2007, Stafford et al. 2005 e 2003, Marshall, 1977; Vowles, 1976). To measure the pain-induced distress caused by dehorning or disbudding plasma concentration of cortisol have been used more frequently than any other parameter (Boandl et al., 1989; Taschke and Folsch, 1993; Wohlt et al., 1994; Cooper et al., 1995; Morisse et al., 1995; Petrie et al., 1996; Sylvester et al., 1998; McMeekan et al., 1997, 1998; Graf and Senn, 1999; Grondahl-Nielsen et al., 1999; Sutherland et al., 2002), but Stilwell et al. in 2010 confirm that cortisol is not a good indicator of pain. Substance P is a neurotransmitter of pain used for the first time in cattle in 2008 by Coetzee et al. who found that substance P is a better indicator of pain than cortisol in calves after castration or simulated castration. On these basis we hypothesized that SP could potentially be a more specific measure of pain in cattle undergoing disbudding than would the plasma cortisol response, but the methods to measure its concentration in cattle plasma is still to set up, so we are improving it. We studied the effects of true and simulated disbudding on plasma concentration of cortisol in calves undergoing 2 different alpha2-agonists: xylazine and dexmedetomidine. Plasma cortisol concentration has not been an useful method to compare the analgesic features of the 2 alpha 2agonists xylazine and dexmedetomidine. In fact they both act on the plasma concentration of cortisol, increasing it because of their effects on baroreflex and on muscles. In Veterinary Medicine dexmedetomidine is registered only for its utilization on cats and dogs and it is appreciated for its minimal side effects on the respiratory tract, for its remarkable sedative and anxiolytic properties and for the possibility it can be administered by continuous infusion. The utilization of dexmedetomidine in cattle has never been researched right now