The use of farrowing crates is increasingly questioned from an animal welfare point of view. Even so, since a number of attempts to develop loose farrowing systems have been unsuccessful, leading to high levels of piglet mortality due in the main to crushing, many farmers remain sceptical as to whether or not alternative systems can be viable. On the other hand, several European countries have introduced legislation requiring loose farrowing systems, thus promoting research into this type of housing and allowing for performance studies based on large samples of commercial farms. As a consequence of these recent developments, we think it timely to reconsider the evidence available on loose farrowing systems. In our review, we first address the normal peri-parturient behaviour of domestic pigs, as well as studies comparing behaviour and stress physiology in sows kept in both crates and loose systems during farrowing. We then review approaches taken to develop alternative farrowing systems in different countries, and focus lastly on pen, piglet and sow characteristics that contribute to piglet survival in loose farrowing systems. Taking scientific evidence as well as practical experience into account, we conclude that piglet mortality in loose farrowing systems need not exceed that of crate systems. To obtain good performance results, sows due to farrow should be kept individually in sufficiently large pens, structured for preference into a nest area and an activity area. Furthermore, both management and breeding aspects, resulting in high piglet viability and good maternal behaviour, are essential to achieve high production in loose farrowing systems.

A number of alternative farrowing systems have recently been developed, some of which have been more successful at improving welfare and productivity than others. It is argued that for a system to be successful it should meet with the behavioural requirements of the sow at this time. A number of studies have been carried out to observe the natural behaviour patterns of the peri-parturient sow in a wide range of environmental conditions. These studies have shown that during each phase of peri-parturient behaviour there are a number of key environmental features and conditions which are important to the sow. These include the social environment, shelter, nesting material and offspring interaction. This information can be useful in the design of farrowing systems. A review of the literature indicated that the more these conditions are met, the more readily the sow can adapt to the system, leading to improvements in maternal behaviour and piglet production.