Analgesic effects of morphine and butorphanol in broiler chickens.

OBJECTIVE: To evaluate analgesic efficacies of morphine and butorphanol in lame broiler chickens.

STUDY DESIGN: Double blind, randomized, controlled experimental study.

ANIMALS: In study 1, 36 lame and 36 sound chickens. In study 2, 48 lame and 48 sound chickens.

METHODS: Sound and lame chickens were gait scored and randomly assigned into four groups: sound-drug, sound-placebo, lame-drug, and lame-placebo in study 1. In study 2, an additional lame and sound handling control group was included. Chickens in drug groups were injected with either morphine or butorphanol 2 mg kg-1 intravenously. Chickens in placebo groups were injected with an equal volume of normal saline. All birds underwent an obstacle course (OC) and latency-to-lie (LTL) test before injection and at 30 minutes and 2 hours after injection, to assess their walking ability and their standing ability. The time taken to finish the OC and the standing time in the LTL test were recorded. Friedman tests with Dunn's correction were used to identify significant differences.

RESULTS: Lame chickens finished the OC faster (mean ± standard deviation 36 ± 8 c.f. 69 ± 18 seconds) after the injection of butorphanol. Morphine caused sedation with an increase in time taken to finish the OC, even in sound chickens. In the lame handling control and placebo groups the OC times increased and the LTL times decreased with each observation.

CONCLUSION: Intravenous butorphanol (2 mg kg-1 ) may be analgesic in chickens for up to 2 hours. Morphine caused sedation.