The use of a medetomidine, butorphanol and atropine combination to enable blood sampling in young pigs

Abstract AIM: To determine the suitability of a reversible, injectable anaesthetic combination including medetomidine, butorphanol and atropine to produce the degree of immobilisation required to allow blood sampling in young pigs. METHODS: Twenty 6-week-old crossbred, intact male pigs were sedated with an intramuscular (I/M) injection of 80 µ'g/kg medetomidine, 200 µ'g/kg butorphanol and 25 µ'g/kg atropine. Heart and respiratory rates and rectal temperatures were monitored. Excessive salivation, gagging, laryngeal reflex, presence of pedal reflex and deep and surface analgesia were noted. Time of injection and the time when pigs reached mild and full sedation were also recorded. RESULTS: Mild sedation was produced in 90% of pigs after 5.6 (SEM 0.96) min (n=18; median 5, range 2–16 min), and full sedation (lateral recumbency and loss of jaw tone) in 60% of pigs after 12.5 (SEM 2.14) min (n=12; median 10, range 5-28 min). The depth and duration of sedation were very variable and most animals were easily aroused. Ninety percent of the animals required the administration of halothane by mask to allow blood sampling, but the amount of halothane required was small. Heart and respiratory rates decreased (p<0.001) but remained within the normal range. Rectal temperature was above normal at the time of sedation and at the time of blood sampling when the ambient temperature was 29° C but not when the ambient temperature was reduced to 25°C. CONCLUSIONS: The combination of medetomidine, butorphanol and atropine at these doses produced sedation of variable depth and duration that was insufficient on its own to allow blood sampling in the majority of pigs. Hyperthermia can occur in temperature-controlled environments when using medetomidine, butorphanol and atropine in pigs. Reduction of stress and a quieter environment may improve the effects of the anaesthetic combination. KEY WORDS:: Anaesthesiapigsmedetomidinebutorphanol Acknowledgements We would like to acknowledge the contribution of Dr Frank Cross in the planning and execution of this trial, and thank the Institute of Food, Nutrition and Human Health at Massey University for their financial support.