Science of Ethology, Volume 1, Issue 7

Several scientific studies and reviews have compared the welfare benefits of stall versus group housing for gestating sows (1, 2, 3).  The conclusions of these studies vary because welfare assessment involves a variety of measures, and the conclusions reached will vary depending on the emphasis placed on different measures. The key measures and results of studies comparing sow welfare in stalls and groups are summarised below under the headings: sow health and performance, stress physiology, sow behaviour, and sow aggression. Evaluation of the welfare of sows must consider all and not just some of these factors, and the results show that there are advantages and disadvantages to both stall and group housing systems.

For example, a 1997 EU report on sow housing (4) indicated that managing sows in stalls has some welfare advantages, “since pigs are not mixed, fighting with associated injuries is prevented, each sow receives the full ration of food available to her, sows can all feed at the same time, caretaking is made easier and signs of morbidity, such as feed refusals or vulval discharge, are easy to detect.” However, the report goes on to list several disadvantages to sow stalls, including high levels of stereotypies, unresolved aggression and inactivity, weaker bones and muscles, and reduced cardiovascular fi tness. The report goes on to state that, “Some serious welfare problems for sows persist even in the best stall-housing system.” On the other hand, the report lists advantages related to group housing, including increased exercise, greater control over the environment, opportunity for normal social interactions and opportunities to root or manipulate materials (4). As a consequence, group-housed sows show less abnormal bone and muscle development, less abnormal behaviour, fewer health problems associated with inactivity, and better cardiovascular fitness.  However, it is widely recognized that the main disadvantage of group housing is that injuries can occur due to fighting and/or slipping on the floor. Fighting or injury can lead to embryo loss in extreme cases, and detection of health problems is more difficult in groups. The report concludes that, “an enhanced emphasis on good stockmanship and good group housing system design is necessary to prevent these adverse affects.”