The provision of environmental enrichment for pigs, in the form of objects or substrates, is a legal requirement throughout the EU. Environmental enrichment may be defined as an improvement in the welfare of an animal, as measured by psychological and physiological means, as a direct result of alterations in the animal’s environment (Newberry, 1995). Previous studies investigating the use of enrichment objects have tended to focus either on one age group or on the provision of one object throughout the animals’ lifetime (e.g. Beattie et al., 1995; Durrell et al., 1997; Hill et al., 1998; Lyons et al., 1995). This experiment therefore addressed the question of whether pigs of different ages require different types of enrichment objects in order to promote and maintain exploratory behaviour. Straw is generally recommended as suitable enrichment for pigs. However, over 85% of pigs in the EU are housed in slatted systems where it is impossible to use these materials spread over a wide area of solid floor. In these systems it is more typical to use alternatives such as hanging objects and, in such situations, enrichment becomes a single point within the pen rather than a diffuse source. This experiment aimed to identify how a pig’s age affected the extent and synchrony of use of different environmental enrichment materials, and how this use changed over time. In order to measure synchrony it is necessary to determine if more than one animal is performing the same behaviour at the same time, and also to determine whether or not this has simply occurred by chance (Engel and Lamprecht, 1997). Animals behaving independently of each other may still be performing the same behaviour, at the same time, and such chance occurrences need to be factored into calculations to determine the extent of true synchrony (Rook and Penning, 1991; Engel and Lamprecht, 1997). Ten diverse novel objects were each presented to three replicate litters of 3 weeks of age (sucklers) and three replicate groups of three animals of 5 (weaners) weeks and 13 (growers) weeks of age. Video recordings were made of the pigs’ behaviour over a period of 5 days and subsequently analysed for activity, inactivity and object directed behaviour of three animals per group on days 1 and 5. The observed performance of any given behaviour, when at least one other member of the group was also performing that behaviour, was compared with the probability that such concurrence occurred by chance and these results were used to calculate the degree of synchronisation. Gender had no effect on the duration of object use or approach latency. Growers displayed a shorter latency to approach the objects initially compared to sucklers and weaners. Sucklers used the objects to a much lesser extent than either the weaners or growers. Overall object use decreased between days 1 and 5. All of the age groups synchronised their behaviour to a much greater extent than expected by chance. The sucklers showed a higher degree of synchrony of activity and inactivity, but lower degree of synchrony for object directed behaviour, than the weaners and growers. The degree of synchronisation of object directed behaviour decreased over the 5-day period, irrespective of age. Significant correlations were found between the degree of synchrony and extent of object interaction only for the sucklers. Since pigs showed behavioural synchronisation, object availability should be considered when providing desirable enrichment in order to avoid excessive competition in larger commercial groups.

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