Introduction

Gestation sow housing continues to be a contentious issue in North America and Europe. As North American indoor production systems developed in the 1960s and 1970s, sows moved not only indoors, but often into individual housing systems, most typically crates or tethers.

The pressure to move sows from individual gestation crates to gestation pens is being promoted by humane activists and by some niche-market producers. Most North American pork producers have resisted changing from gestation crates to pens to date, but with the success of state-by-state referenda being passed, producers may not have a choice. Florida, Arizona and Oregon have banned individual housing of pregnant sows by public referenda or by legislative action. Other states are considering a ban on gestation crates for sows.

More importantly, selected market-savvy pork producers have recently announced that they will phase out the use of gestation crates and phase in group housing, which has started a 'phenomenon' (ex., Smithfield in January, 2007). This phenomenon may be viewed as a series of dominoes that will fall in a chain reaction that will change the look of modern pork production. Because sow housing is not the only issue of concern to activists, the industry must educate itself on the current science of all animal welfare issues, and current concerns of activists. Current concerns of retailers who, through intermediaries, buy your products and then interact with end-users are perhaps the most important target stakeholder to educate.

To summarize where this paper is going, the authors first provide a history of the gestation crate, then review the science of sow welfare housing system comparisons, then point to potential animal welfare issues when sows are moved from an individual system to group system. Finally, they suggest the industry be proactive in the development of cost-effective alternatives to contentious animal welfare issues and implement change before markets force the industry to make costly changes that may not be in the best interest of pig welfare and sustainable production system.

Modern History of the Downfall of the Gestation Crate

The first time a sow gestation crate appeared in the popular pig press was in December 1969 (a picture of a sow in a neck tether appeared in October 1969) in National Hog Farmer. When the North American swine industry consolidated in the 1990s, the overwhelming majority of sows were moved to gestation crates. This period was significant in the development of the pig industry because:

1. it was a time of rapid expansion and modernization
2. farms were predominantly large in scale and indoors
3. 100 per cent artificial insemination became common practice, and
4. the most common sow housing system was the gestation crate.

After the market crash of late 1998 and 1999, we have not seen such a period of rapid expansion. The facilities built in the 1990s will most likely depreciate over a 20-year span, thus the financial motivation to change housing systems among 1990s-era farms is very low at this time. For facilities that were built before 1990 – many North Carolina farms built in the 1970s and 1980s – many of these facilities may be 20 years old or more, and thus these farms have impetus to remodel.

At the January 2001 meeting of the Manitoba Swine Seminar, Dr McGlone spoke on the issue of gestation sow housing. At that time, McDonald's restaurants were asking the pork industry to explore alternatives to the gestation crate but this was just the beginning of a period of change. In 2003, the EU banned the gestation crate on new farms, and all EU farms must eliminate gestation crates by 2013. In the EU and in current USA programmes of group housing of sows during gestation, they may be in stalls for the first 35 days (approximately) until pregnancy is confirmed.

The US legislature has not considered any national on-farm welfare law for commercial pigs. Activists may favour a national law but the USA congress is not so interested, thus activists have moved to a state-by-state approach, which has proved more effective.

The sow gestation crate has now been banned by popular referendum or by legislative action in Florida, Arizona and Oregon. California, Colorado and other states are actively considering banning sow gestation crates at this time.

The next major historical point came on January 25, 2007 when Smithfield – the largest pork producer in the world – announced that it would phase out the gestation crate in company-owned farms over the next 10 years. In December 2007, pork producers in Colorado made a similar announcement that they would phase out gestation crates for sows over the next 10 years. These announcements and laws mean that over 25 per cent of US pork production is now committed to moving from gestation crates to pens. Although the activists can claim victory here, it was pressure from retailers that drove the industry to give its customers what they want. When our ultimate customers want our product produced in a certain way, it usually makes good business sense to give them what they want (even if it is not totally logical).

Sow Housing Systems - Comparisons

Four major reviews of sow housing systems have been published. Three of the four reached the same conclusion – that sow welfare is equivalent when sows are in well managed crates or pens. In McGlone et al., 2004, the authors conducted a meta-analysis of all of the published data that compared reproductive performance of sows in gestation crates with sows in group pens. A summary of that work is found in Table 1.

We see from Table 1 that the reproductive performance, behaviour and stress hormone levels were not different for sows kept in gestation pens or stalls.

Key Issues in Group Housing: Social Stress and Space

Group housing systems are extremely complex, and difficult with which to come to grips, simply because there are so many factors that must be considered and integrated. Unfortunately, these factors do not always fit together perfectly or even acceptably, simply because they were not designed in the first place to fit together in the present arrangement. Group housing systems are like jigsaw puzzles. Among the many pieces to be put together we have (but not limited too): group size, floor space allowance, group management (static versus dynamic), feeding systems, flooring type and bedding, and many more factors. But these factors alone influence one another, especially the social dynamics of the group pen.

As empirical observations and experimental data accumulate, it is clear that each factor and each system has advantages and disadvantages in terms of productivity, profitability, and yes, even animal welfare. All current group-system alternatives allow sows freedom of movement, opportunity for social interaction, and individual choice among available microenvironments, but there are greater or lesser welfare problems associated with each of these group-housing systems, including stress due to aggression early on and social tension for the duration.

The question remains: how can we minimize aggression and competition among group-housed sows? The most serious and injurious aggression and competition among group-kept sows occurs upon introduction of new sows to a group (mixing) and at feeding-time. Upon mixing, sows will fight with a high level of aggression, part of their natural attempt to form a new dominance hierarchy. The aim of sow management must be to enable the formation of the social order with as little stress and physical injury as possible.

Still, in many layouts, a sow's ability to retreat and protect itself is limited. A number of excessively fat sows may occur due to over-eating by dominant sows, as well as a number of very thin sows may develop due to reduced feed intake by low-ranking, submissive sows. Moreover, this increased fighting can result in vulva biting skin lesions and wounds on rump, shoulders and other regions of the body as well as lameness.

In loose accommodation with relatively large space allowances and few places for sows to get 'cornered' by an aggressive groupmate – there are the options of large groups with sows entering and leaving the group each week (dynamic group management); weekly service groups which stay together throughout pregnancy (static group management); smaller groups with each weeks sows broken up into a number of subgroups; and/or a combination of these, each used at different stages of pregnancy.

Group housing often increases the rates of sow scratches and skin lesions. One recent paper (Salak-Johnson et al., 2007) measured sow body condition, skin lesions and sow performance when sows were in crates or pens with between 1.4 to 3.3 m² per sow (15, 25 or 35 ft² per sow in a pen of 5 sows).

The Illinois scientists found that sows were fatter but had lower body weight when in crates than in group housing (Table 2). They also found an increase in the rate of skin lesions for group-housed sows compared with individually crated sows, some of which had been in crates for multiple pregnancies.

While the Illinois group started their work with mixed-parity sows, Hulbert and McGlone (2006) started their study with gilts that had developed in the same social groups. Fighting was minimal and group-housed and crated sows had statistically similar rates of lesions (and the numbers of lesions were very low).

Recent research publications comparing individual housing and group housing reminds us that group housing is not as simple as taking sows out of the crates and mixing them in group pens. A higher level of stockmanship must be employed including consideration of development of gilts and young sows in social groups that remain together as long as possible so that social stress can be minimized.

What is Next?

* "Premiums will probably always be provided for products with real or perceived improvements in pig welfare compared with commodity products"

While it might have seemed an odd statement to believe the gestation crate would not remain an industry standard in 2001, today it seems clear that the industry must move away from individual crating of pregnant sows and towards group housing. However, sows may be kept individually in stalls for the first few weeks after breeding until they are confirmed pregnant and they may be kept in locked feeding stalls for a few hours a day during feeding, which will better manage sow feed intake and decrease body condition variation.

The movement away from gestation crates is fully underway. Early adopters will gain easier market access and perhaps some premium markets will prefer pork from farms that use group housing rather than individual housing of sows. As more of the industry adopts group housing, it will quickly become the norm and no premium will be given. Premiums will probably always be provided for products with real or perceived improvements in pig welfare compared with commodity products.

Stockmanship skills will need to be learned or re-learned for some workers who have not managed group-housed sows. Research studies indicate that well managed group housing systems can work as well as individual housing systems.

Group housing systems require a bit more space and so there is an economic cost associated with group housing both in the cost to convert and in variation in productivity if a higher level of stockmanship is not available.

The individual crate system as it stands today has to be changed to become more acceptable to some consumers. However, a modified individual system such as the free access stalls can work well. Housing systems that have both individual and group interaction opportunities will be a reasonable outcome that satisfies animal welfare concerns and provides protection for submissive sows during feeding and during early pregnancy.

The activists and market forces have shown how they can shape the industry. It is time for the industry to do some soul-searching to discover other areas of animal welfare concern and to develop a proactive approach of research and implementation of findings to get ahead of criticism and to take advantage of market forces that care about farm animal welfare.

Literature Cited

Hulbert, L. and J.J. McGlone. 2006. Evaluation of Drop vs. Trickle Feeding Systems for Crated or Grouped Penned Gestating Sows. J. Anim. Sci. 84:1004-1014.
McGlone, J.J., E. von Borell, J. Deen, A.K. Johnson, D.G. Levis, M. Meunier- Salaun, J. Morrow, D. Reeves, J.L. Salak-Johnson and P.L. Sundberg. 2004. Review: Compilation of the scientific literature comparing housing systems for gestating sows and gilts using measures of physiology, behavior, performance and health. Professional Animal Scientist. 20:105-117.
Salak-Johnson, J.L., S.R. Neikamp, S.L. Rodriguez-Zas, M. Ellis and S.E. Curtis. 2007. Space allowance for dry, pregnant sows in pens: Body condition, skin lesions, and performance. J. Anim. Sci. 85:1758-1769.

March 2009