Larsen, M. L. V., Jensen, M. B., Pedersen, L. J. 2019. Increasing the number of wooden beams from two to four increases the exploratory behaviour of finisher pigs. Applied Animal Behaviour Science 216, 6-14.

Pigs are highly motivated to perform exploratory behaviour and must have permanent access to manipulable material according to the EU Directive 2008/120/EC. A commonly used type of manipulable material is wooden beams. The beams are placed in vertical racks and touch the floor. According to Danish implementation of the directive, at least two wooden beams should be provided to a pen of 10–18 finisher pigs. However, it has not been investigated whether access to a higher number of wooden beams benefits pigs by stimulating more oral manipulation. The aim of the current study was to investigate the effect of increasing the number of wooden beams from two to four in pens of 18 finisher pigs. Response variables were manipulation of wooden beams including bout frequency, bout duration, hourly duration, proportion of pigs manipulating within the hour and proportion of pigs manipulating simultaneously. Behaviour was observed from video on a fixed weekday in weeks 2, 4, 6 and 8 of the finisher period. The effects of number of beams, beam location, observation week and pigs’ introduction weight were analysed. Increasing the number of beams from two to four increased the bout frequency, average bout duration, hourly duration of manipulating the beams and the proportion of pigs manipulating within the hour; however, it did not increase the proportion of pigs manipulating simultaneously. Only bout frequency decreased with time, and this decrease was seen later in pens with four beams. Thus, four compared to two beams increased the exploratory behaviour of the pigs, the number of pigs engaged in the manipulation and kept the pigs interested in the beams for longer. In pens with four beams, beam location also affected beam manipulation with a higher bout frequency on beams located on the opposite side of the pen as the feeder. Pigs’ introduction weight did not affect pigs’ manipulation of the beams. The results suggest that the pigs benefit from being provided with a higher number of beams than currently demanded by the Danish implementation of the EU Directive.