Effect of marginal environmental and social enrichment during rearing on pigs’ reactions to novelty, conspecifics and handling

Abstract

The rearing environment of farmed animals can affect their behaviour when handled, and therefore needs to be taken into account when selecting for traits such as docility. Therefore, 126 German Landrace and Pietrain×German Landrace pigs were reared in two different production environments (barren (n=47) or slightly enriched (n=79)), both corresponding to commercial conditions. The marginal enrichment included the provision of more toys, an additional feeder type, and a larger number of conspecifics, while space allowance per pig remained equal. Pigs’ responses to (a) a novel arena test (NAT), (b) a novel object test (NOT), and (c) weighing, were compared, together with the number of skin lesions (an indicator of aggressiveness). While the differences in behaviour in the NAT were not significant (p>0.1), the differences in the other tests were significant. In the NOT enriched housed pigs contacted the novel object more frequently (p=0.0124) and showed a tendency for a greater total duration of manipulating the novel object (p=0.0641). Furthermore, the pigs housed in enriched environment were calmer at loading onto the scale (p=0.0008), but more agitated on the scale (p<0.0001). Barren housed pigs had more severe skin lesions (p=0.0074). Correlations between scores from the behaviour tests and the daily weight gain were not significant. However, correlations between the behaviour patterns measured in the tests revealed that pigs which showed more activity in the NAT and NOT were also more active in the other tests. Results indicate that marginal changes in the housing environment affect the behaviour of the pigs. Overall, the activity of barren housed animals seemed to be reduced, as revealed by the behaviour tests. Therefore, the housing environment must be taken into consideration carefully when evaluating the behaviour or indicator traits such as skin lesions for selection purposes in pigs. In addition, results of the present study have implications for animal welfare, showing that marginal enrichment of rearing environment leads to changes in behaviour that may partially be related to improved cognitive and/or physical development of the pigs.