As it is edible, it is attracive to chew on. As an additional plus, it provides pigs with fibre, which often is scarce in ordinary pig feed.
Straw has to be clean, however. Pigs are not interested in dirty straw.
If the pen has a solid floor, enabling the use of a thick layer of straw on the floor, this gives pigs an opportunity to root and to build nests for resting, which also is one of the natural behaviours of pigs. Additionally, a sufficient layer of straw on the floor improves comfort while laying down by cushioning the floor. During the cold part of the year, it also helps as insulation on the cold concrete floor.
In pens with partly or fully slatted floors, it still is possible to obtain part of the benefits straw can provide. The most common solutions are straw racks or manually distributing small amounts of straw. When constructing a new building or renovating an existing one, automatic dispensing systems for straw are a good option to consider.
According to a previous study mapping risk factors for tail biting on Finnish pig farms, tail biting is more common on farms with partly or fully slatted floors than on farms with solid floors. One of the reasons is likely to be the larger amounts of straw in the latter.