Stalls or Groups: It’s a Complex Issue [edited]

October 17, 2012 — 

Rob Knox, University of Illinois researcher, looked at the production and welfare impact on sows in various housing arrangements. This year, numerous food retailers have announced deadlines for their pork suppliers to ensure that farms raising the hogs eliminate gestation-sow stalls. These directives are vague in details regarding the compliance regulations, verifications and allowances.

The truth about animal housing, welfare and production is complex. In fact, simply moving sows from stalls to pens where they can move around will definitely not improve their welfare. Sows were moved into stalls decades ago to improve welfare by ensuring that they had access to daily feed, to eliminate fighting and to provide individual care and reproductive management. When sows moved into stalls it took years to develop experience and expertise.

This education occurred for veterinarians, producers, building designers and equipment manufacturers as well as scientists. Improvements in stall housing occurred in flooring, crate design, feeding, watering and air-control systems. The result has been dramatic improvements in reproductive performance and overall animal health.

owever, stalls do restrict sows’ freedom of movement and have been associated with lesions and feet and leg problems. Some of these problems have been addressed with improvements in crate design, flooring, genetic selection and diet/nutrition.

One serious concern that producers have, but which receives little attention from food companies or animal activists, involves reproductive losses after mixing sows in groups. In fact, there is data to support reproductive problems, such as conception failure, pregnancy losses and lower pigs born alive in sows mixed into groups. This problem may be more pronounced when mixing occurs at certain stages of pregnancy and certain seasons of the year.

Reproductive failure subsequent to mixing sows in groups is presumed to be related to stress. To avoid such problems, producers have been reluctant to move sows at sensitive times, such as during early embryo development and implantation.

A review of the scientific literature on this is quite controversial and the data is limited. But one can find research that reports reproductive failure in pregnancy loss, reduced embryo survival and fewer pigs born.

In contrast, there are just as many studies showing no effect from day of mixing or group housing. However, almost all studies show that mixing sows, regardless of the system, causes some form of stress and fighting.

While there’s no fighting, fewer lesions and scratches, and no competition for feed in stalls, there are other challenges. Some reports suggest that restricted movement produces long-term chronic stress, resulting in increased lameness. In groups, sows fight to establish dominance, which increases stress, lesions and lameness in the period soon after grouping.

As time passes, the social order is established and there are fewer fights and associated problems. However, the stresses and injuries persist and can cause long-term damage and force premature culling.

An alternative system approved in Europe includes using stalls in early gestation, followed by relocation into group pens. Other systems provide free-access stalls with a common pen area, letting sows choose where to go. This system works well but is costly for space and equipment. It’s interesting that sows often choose to be in their stall. However, individual preferences may be related to social rank, as well as the pen size and design.

Many European producers lobbied for and were allowed to use stalls during the first four weeks after breeding. But some countries are cutting that time down to four or five days. U.S. producers are concerned about the effects of mixing on both sow reproduction and welfare, which led to an NPB-funded study that we conducted at the University of Illinois.

The stall seems to be an important tool for production and welfare and provides benefits with strategic use in early pregnancy, with pen housing at a later stage. Full consideration of all options is important to helping producers meet the animal welfare and productivity needs.

Testing the Mix

To evaluate the impact of mixing sows following breeding, University of Illinois researchers investigated various options. The study was conducted on a 6,000-sow, commercial research farm in the Midwest and measured reproductive performance and animal welfare. The four mixing options included: 1.Housing sows in stalls throughout gestation. 2.Housing sows in stalls until mixing into groups of 58 sows on days three to seven of gestation. 3.Housing sows in stalls until mixing into groups on days 13 to 17 of gestation. 4.Housing sows in stalls until mixing into groups after day 35 of gestation.

As many previous studies have shown, the best reproductive and welfare measures were associated with housing sows in stalls. Sows mixed into groups on day 35 of pregnancy performed most similarly to stalls in long-term reproductive measures for conception and farrowing rate, and for the proportion of sows that remained in the herd to produce another litter. However, welfare measures were the poorest for those sows in the weeks after mixing, due to increased fighting, stress, lesions and lameness. But most of those measures improved in the long term.

Mixing sows in the first week after breeding reduced conception and farrowing rates, as well as the proportion of sows remaining to produce another litter compared to sows in stalls. These early-mixed sows showed more fighting, lesions and lameness in the short and long term compared to other treatments. For sows that were mixed on days 13 to 17 post-breeding, conception rates declined but farrowing rates did not differ from those in stalls. However, fewer of these sows remained in the herd to produce another litter. Welfare measures in this group showed the least fighting, stress lesions and lameness compared to the other mix treatments. Over the long term, most measures were similar to those in stalls.

Overall, there was no effect of any treatment on the number of pigs born alive. Considering the combined reproduction and welfare measures, the study indicated that stalls were the best option, followed by mixing sows after day 35. Mixing during the first week of pregnancy should be avoided for both reproductive and welfare reasons. However, there may be some potential benefit to mixing after days 13 to 17 but before day 35.

Source: Porknetwork.com, October 8, 2012
By: Rob Knox, swine specialist, University of Illinois Extension