XYLAZINE AND A XYLAZINE FENTANYL CITRATE/AZAPERONE COMBINATION IN FARMED DEER .1. DOSE-RATE COMPARISON/

Six 1-year-old farmed red deer were used to compare physiological and behavioural responses to a range of doses of 5% xylazine with or witho ut the addition of 0.4 mg of fentanyl citrate and 3.2 mg of azaperone per mi. Each deer was randomly assigned to one of six treatments: xyla zine alone at 0.4 and 0.6 mg/kg, the xylazine/fentanyl citrate/azapero ne combination containing 0.2, 0.4 and 0.6 mg/kg of xylazine, or a ste rile water control. Injections were given intramuscularly in the anter ior neck, operator blind, on each of 6 sampling days between October a nd January, such that each deer received all treatments with 9-28 days between each treatment. Measurements included heart rate and respirat ion rate. A 0-3 scoring system (normal to nil response, respectively) was devised to record sedative responses (body stance, head position, degree of eye closure, palpebral reflex, resistance to movement of the head, response to noise) and analgesic responses to touch and pinchin g of the ear, and response to a needle prick in the gluteal region. Sc ores were added to produce a sedation score and analgesia score, respe ctively, for each treatment. Records were taken immediately prior to i njection and thereafter at 5, 14, 25, 35, 60, 90, 120, 150, 180, 210, 240 and 300 minutes. All deer given each dose rate of the xylazine and the xylazine/fentanyl citrate/azaperone combination became recumbent. There was a tendency for the time to recumbency and variation of time to recumbency to be shorter at higher dose rates and with the additio n of fentanyl citrate and azaperone to xylazine, particularly with xyl azine at 0.4 mg/kg. These trends were not statistically significant (p >0.05). The duration of recumbency was shorter with the low dose of th e xylazine/fentanyl citrate/azaperone combination (0.2 mg/kg of xylazi ne) than for the higher doses of xylazine alone or the combination of drugs (p<0.05). There were no significant differences in heart rates o r respiration rates between treatments, although all treatments signif icantly reduced both heart and respiration rates (p<0.01). The sedatio n scores showed similar peak responses and timing to peak responses (1 4-25 min) to both drug treatments and all dose rates, but the response s were less persistent for lower doses. The analgesia scores showed a similar pattern, with peak responses 14-35 minutes after administratio n and more persistence at higher dose rates of both xylazine alone and the xylazine/fentanyl citrate/azaperone combination. This study has s hown that most physiological and behavioural responses to a range of d oses of xylazine or the xylazine/fentanyl citrate/azaperone combinatio n were statistically similar. However, there was a tendency for recumb ency to occur more rapidly and with less variation in timing when the mid-range dose of the drug combination was used, supporting the observ ation by practitioners that the drug combination results in a more rap id and reliable state of recumbency at a lower dose rate of xylazine.