Enrichment use in finishing pigs and its relationship with damaging behaviours: comparing three wood species and a rubber floor toy

Environmental enrichment in pig housing is a legal requirement under current EU legislation, but some recommended loose materials may cause obstructions in fully-slatted systems. Wood is an organic material that could be compatible with slatted systems. This study investigated enrichment use in finishing pigs (three wood species and a rubber floor toy) and explored the relationship between use and damaging behaviours, and physiological and physical measures of stress and injury. Individual variation in enrichment use within pen was also investigated. Pigs (12 weeks old; week 0) were housed in 40 pens of seven pigs (n = 280). One of four different enrichment items (one spruce, larch, or beech wooden post, or rubber floor toy) was randomly assigned to each pen (10 pens/treatment). The behaviour of each individually marked pig was observed continuously from video recordings taken on six different occasions (twice during week 2, 4 and 7; 1 hour per occasion). Individual tail/ear lesion and tear staining scores were recorded every 2 weeks. Saliva samples for cortisol analysis were obtained from three focal pigs per pen every 2 weeks. These focal pigs were selected based on the latency to approach the experimenter on the first sampling day and classified as 'Approach', 'Neutral' or 'Avoid'. Carcasses were inspected for tail lesions and potential oral damage. Time spent using enrichment was higher in pigs with spruce and rubber toy than with larch and beech (P < 0.001). Spruce was used up the most quickly and was the softest of the wood species (P < 0.001). High use of spruce was not due to consistent high use by certain pigs. No treatment effect on any other behaviour was recorded, but enrichment use was positively correlated with damaging behaviours at pen level (P < 0.001). Spruce pigs had slightly more severe tail lesion scores than Beech (P < 0.05). Salivary cortisol did not differ between treatments but was higher in 'Avoid' than 'Approach' pigs (P = 0.04). No clear oral damage that could be attributed to using wood was found. By investigating enrichment use at both pen and individual level, a more complete picture was obtained of how pigs used the enrichment. Wood appears to be a safe material to use as environmental enrichment for pigs and a softer wood species was preferred by pigs with equal preference for the rubber floor toy.