Evaluation of a behaviour protocol for use in recording the behaviour of horses following administration of methadone

Abstract: There is a need for correct and adequate pain assessment in horses. Methadone is used in pain management in horses but the full pharmacokinetic picture of methadone is not yet known. The aim of this pilot study was to develop a behaviour protocol and suggest a reliable recording method for use in a larger research project with an aim to potentially correlate behaviours to concentration of methadone in blood. In this study two coldblooded trotters were given methadone intravenously with doses of 0.1 mg/kg for horse 1 and 0.2 mg/kg for horse 2. The horses were videotaped pre and post methadone administration. A behavioral protocol, with the purpose to find behaviours that were performed, was developed and evaluated. Following that different recording methods were tried to find the optimal recording method. The results showed that horse 2 had a pronounced peak in locomotory behaviour post methadone. Foraging behaviours had distinct peaks post methadone administration in both horses. Poor coordination was only seen twice and only in horse 2. Both horses scratched post methadone administration and this behaviour appeared frenzied at times. Instantaneous sampling with 10 second intervals was found to be the most rational way of observing behaviour. Instantaneous sampling and continuous recording could both be used during the same observation session, but it is suggested that the amount of time spent on continuous recording is standardized.