There are now many comparative studies in the animal science literature that document differences in production performance, behavior, and welfare indications between animals housed in gestation crates and those housed in pens. One of the most often-cited studies was carried out by McGlone et al. (2004). This study aggregated research findings from 35 previous comparative studies to determine whether sow behavior, performance, or physiology differed between the two housing types. The study tested for statistical differences between farrowing rates; pigs born per litter; oral, nasal, and facial behaviors;5 and cortisol blood levels 6 in gestating animals. The research results, which are summarized in the table below, indicate that the differences between the means of measured variables were not statistically significant. That is, none of measures were significantly (P<0.05) influenced by sow housing type. The study concludes that “gestation stalls or well-managed pens generally … produced similar states of welfare for pregnant [females] in terms of physiology, behavior performance, and health.”
This study also addresses two issues important in comparing the different systems. The study indicates that sow productivity—as measured by farrowing rates and pigs per litter—is not affected by housing type. This is good news to for U.S. pork producers, some of whom equate group housing with lower female productivity and lower asset returns. More important perhaps, the study identifies the producer’s animal handling/management skills as the key to maintaining productivity of sows housed in pens.
With respect to concerns about the effects of gestation crate housing on animal welfare, neither McGlone et al., nor current animal science research generally provide clear, empirical evidence that switching to group housing improves the welfare of pregnant female swine. The literature is supportive of the contention that sow/gilt welfare is not determined by housing type. “In other words proper design of stalls and pens can result in equivalent animal performance and welfare outcomes, although the design features for achieving that objective will differ. Therefore, it’s not clear that simply switching to group housing will inherently improve or reduce sow performance or welfare.”