Comparative analgesic efficacy of morphine sulfate and butorphanol tartrate in koi (Cyprinus carpio) undergoing unilateral gonadectomy.

OBJECTIVE: To identify pain-related behaviors and assess the effects of butorphanol tartrate and morphine sulfate in koi (Cyprinus carpio) undergoing unilateral gonadectomy. Design-Prospective study. ANIMALS: 90 adult male and female koi. PROCEDURES: Each fish received saline (0.9% NaCl) solution (which is physiologically compatible with fish) IM, butorphanol (10 mg/kg [4.5 mg/lb], IM), or morphine (5 mg/kg [2.3 mg/lb], IM) as an injection only (6 fish/treatment); an injection with anesthesia and surgery (12 fish/treatment); or an injection with anesthesia but without surgery (12 fish/treatment). Physiologic and behavioral data were recorded 12 hours before and at intervals after treatment. RESULTS: Compared with baseline values, the saline solution-surgery group had significantly decreased respiratory rates (at 12 to 24 hours), food consumption assessed as a percentage of floating pellets consumed (at 0 to 36 hours), and activity score (at 0 to 48 hours). Respiratory rate decreased in all butorphanol-treated fish; significant decreases were detected at fewer time points following morphine administration. In the butorphanol-surgery group, the value for food consumption initially decreased but returned to baseline values within 3 hours after treatment; food consumption did not change in the morphine-surgery group. Surgery resulted in decreased activity, regardless of treatment, with the most pronounced effect in the saline solution-surgery group. Changes in location in water column, interactive behavior, and hiding behavior were not significantly different among groups. Butorphanol and morphine administration was associated with temporary buoyancy problems and temporary bouts of excessive activity, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Butorphanol and morphine appeared to have an analgesic effect in koi, but morphine administration caused fewer deleterious adverse effects. Food consumption appeared to be a reliable indicator of pain in koi.