Hutson, G. D., Haskell, M. J., Dickenson, L. G. et al. 1993. Preferences of pregnant sows for wet and dry concrete floors. Applied Animal Behaviour Science 37, 91-99.

The sows in this study showed a clear preference for dry floors. When fed on the dry side sows spent most of their time in the dry pen. In contrast, when fed on the wet side, sows quickly changed their pen occupancy from the wet to the dry side. .. Sows did not sit, kneel or lie on the wet floor, in contrast with the 40-50% of time spent in these activities on dry floors. Thus, these results confirm that at 20C, in a windowless environment, a wet concrete floor is an aversive environment for the sow.