THE EFFECT OF SUBSTRATE-ENRICHED AND SUBSTRATE-IMPOVERISHED HOUSING ENVIRONMENTS ON THE DIVERSITY OF BEHAVIOR IN PIGS

In intensive farming situations, growing animals are housed in relativ ely barren environments. The lack of opportunity to perform substrate- interactive and manipulative behaviour patterns may affect the express ion and organization of these behaviours. However, making direct compa risons of the behaviour expressed in environments of differing physica l complexity is difficult. In this experiment a relative diversity ind ex was used ro compare the behavioural repertoires of pigs housed in t wo different environments for a period of five months. One group of pi gs (substrate-enriched) had straw, forest bark and branches added to t he standard pens and the other group (substrate-impoverished) did not. The pigs were individually housed, and their behaviour was focal samp led in these pens on one day each month. It was shown that the relativ e diversity of manipulative behaviour shown by the pigs in the substra te-impoverished environment was lower than in the pigs in the substrat e-enriched environment (p < 0.05). The relative diversity of the whole behavioural repertoire shown by the pigs in the substrate-impoverishe d environment also tended to be lower than that in the substrate-enric hed environment (p = 0.06). It is concluded that this may be due to a difference between the two groups in motivation to interact with and m anipulate objects, or a function of the manipulable quality of the sub strates available to them. Alternatively, exposure to substrate-impove rished environments may interfere with the ability to express manipula tive behaviour. Both situations pose a threat to the welfare of growin g pigs resident in barren environments.