Rosvold, E. M., Newberry, R. C., Framstad, T. 2018. Nest-building behaviour and activity budgets of sows provided with different materials. Applied Animal Behaviour Science 200, 36-44.
Domestic sows are still highly motivated to build a nest before farrowing. Many pig houses have slurry systems that do not allow use of long straw or other bulky materials that could block the drains...