Effect of Morphine Administration on Social andNon-Social Play Behaviour in Calves.

The objective of this study was to evaluate the effect of morphine on social and non-socialplay behaviour in calves. Twelve calves experienced four treatments in a cross over 2 × 2 factorialdesign: Calves received an intravenous injection of morphine or saline 10 min prior to being testedindividually or in pairs in an arena for 20 min. Play behaviour was continuously recorded in thearena test.