Influence of different types of environmental enrichment on the behaviour of finishing pigs in two different housing systems: 2. Ratio of pigs to enrichment

The aims of this study were to assess the effects of: (1) environmental enrichment with either straw bedding or a hanging manipulable toy and (2) the ratio of pigs to environmental enrichment when toys are provided. One thousand and twenty four (Large White × Landrace) × Large White pigs were housed contemporarily, in 32 pen groups of 32 pigs (16 pens in each housing system), in matched straw-bedded (ST) or fully-slatted (FS) buildings from 35 kg to slaughter at 104 kg liveweight. In the ST building, half of the pens were enriched only by the straw bedding and half received additional enrichment in the form of a single hanging ‘toy’. In the FS house, half of the pens were provided with the same hanging toy, whilst the remaining pens were provided with four such toys. Time spent in toy manipulation was < 2% in both housing systems, and did not differ in pair-wise comparison of the same toy in different housing systems, or the different numbers of the toy per pen within the FS house. Manipulation of straw bedding occupied a much higher proportion of time (21%). In the absence of straw, significantly more investigatory behaviours were directed towards pen components (P < 0.001), with a similar tendency in behaviours directed at pen-mates (P = 0.06). It is concluded that the low level of occupation provided by the hanging toy was unrelated to spatial restriction of access to the environmental enrichment, as there were no differences in the level of pig- or pen-directed behaviours, or in the level of skin lesions, between pigs provided with one or four toys within the FS house.