Researchers at the Prairie Swine Centre (PSC) in Saskatoon, Saskatchewan, tried giving sows the best of both worlds — protected stalls and open lying areas. Their study took a closer look at how sows allocated their time in rooms equipped with walk-in/lock-in, free-access gestations stalls in two different pen configurations.
The first configuration, referred to as the “I” pen, includes a fully slotted, 10 x 35-ft. alley between two rows of 16 stalls (see photo and Figure 1). 
The second configuration, the “T” pen, also has the 10 x 35-ft. alley between two rows of stalls, plus a 12 x 23-ft. loafing area on one end.
Eight groups of about 25 sows were used in the study. Group size was determined by the number of sows confirmed pregnant within a two-week breeding date window. The number of operational, free-access stalls was matched to the number of sows placed per pen. Surplus stalls were locked closed during the trial.
As sows were moved from a breeding stall to a test pen, they were weighed and numbered with paint. Two cameras were mounted above each end of the “I” pen, and four cameras were above the “T” pen areas. Photographs were taken at two-minute intervals for a 24-hour period for 11 weeks of gestation.
Test pens were divided into three areas in the “I” pen and nine areas in the “T” pen, as shown in Figure 1 . The location of each sow was recorded by a trained observer using the photographs. The percentage of time spent outside of the stall and the numerical location of the sows in the free space were recorded.
“The majority of sows (more than 95%) did use the free-space areas, although not on a regular basis or for extended periods of time,” explains Harold Gonyou, PSC research director.
Overall, the average usage of the free-space areas in either pen was relatively low. But the sows in the “T” pens used their free space significantly more than sows housed in the “I” pens.
“More than half of the animals in the study spent less than 5% of their time in the free-space area, but the average was about 18%,” Gonyou explains, noting there was considerable individual variation.
“Heavier sows appeared to use the free-space area considerably more than lighter sows; older, higher-parity sows also used the free space more (Figure 2 ).
Preferred Lying Areas
In the “I” pens, sows preferred to lie in Area 3 (Figure 1 ), but when given the additional loafing area in the T-shaped pen, sows preferred to lie in the corners — Areas 5, 6, 8 and 9 (Figures 3 and 4 ).
“The areas where sows have shown a preference to lie down all have more walls, which can act as support (when lying down),” Gonyou observes. This preference reinforces previous research, mostly in a farrowing environment. In one study, researchers found that 89% of lying events were accomplished using a sloping wall or a wall fitted with a piglet-protection rail.
Future Sow Studies
“Although many sows did use the free space, it was at much lower levels than expected,” Gonyou reinforces. “This could be due to several possibilities, such as lower-ranking animals feeling threatened by higher-ranking sows, or larger sows utilizing the free space due to crowding in the (free-access) stalls.”
The optimum sow housing system will facilitate social interactions and minimize aggression and competition, he explains. Therefore, scientific research is needed to guide the industry toward designs that meet those goals.
“Group housing of sows is recognized as an alternative system for improving animal comfort and well-being. It is apparent that the older, heavier sows are utilizing the space the most. Therefore, further research in this area will involve reducing social stress perceived by younger animals and making the free-space area more comfortable,” Gonyou says.
Program funding for the research project was provided by SaskPork, Alberta Pork, Manitoba Pork Council and the Saskatchewan Department of Agriculture and Food.