Flooring type may have a major influence on thermo-regulatory behaviour in finishing pigs, as well as on the occurrence of skin lesions at their leg joints and pen fouling. In this study, we compared the lying behaviour, pen fouling and the occurrence of leg lesions in finishing pigs kept in partly slatted pens with a concrete lying area covered with either a non-deformable synthetic plate or a small amount of straw (100 g per pig an day), or left bare, whilst controlling for the effects of temperature and pig weight.

Eighteen groups of 10 finishing pigs each were kept in six replicates in three pens with different floor types as described above. Lying behaviour was video recorded for 48 h at weights of <35 kg, 50–70 kg and >80 kg. A fouling score for the lying area was estimated daily. Pigs were examined for skin lesions around the carpal and tarsal joints upon introduction into the experimental pens at a mean weight of 28 kg (±3.9 S.D.) and four times thereafter at regular intervals until they reached 100 kg. Data were analysed using generalised linear mixed-effects models taking the hierarchical experimental design into account.

Floor type in the lying area did not affect the proportion of pigs lying laterally or sternally, or huddling. However, the proportion of pigs lying on the slatted floor was higher in pens with synthetic plate flooring compared to those with a straw layer and was even lower in pens with concrete flooring (p = 0.015). Fouling of the lying area increased as room
temperatures rose. This increase was sharper in pens with straw on the floor than in those with bare concrete flooring (interaction: p = 0.017), but did not differ between pens with a layer of straw and those with a synthetic plate flooring (interaction: p = 0.324). The likelihood of pigs having hairless patches or hyperkeratosis on the carpal joints was similar
in pens with synthetic plate flooring and in those with a layer of straw, but higher in bare concrete- floored pens. This pattern was also found with respect to the higher prevalence of adventitious bursae at the carpal joints and wounds at the tarsal joints found in pigs kept in pens with synthetic plate flooring.

In conclusion, our results indicate that the synthetic plate flooring studied may cause heat-loss problems, and does not improve floor quality in the lying area as regards skin lesions. From the point of view of pig welfare, it cannot therefore be considered a better alternative to bare concrete floors.

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