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(Current as of June 2005) 
Pregnant sows (including gilts) are kept in a variety of
production systems. The industry has moved toward gestation stall
(crate) housing, because gestation stalls increase caregiver
productivity, require lower capital investment, and are easier to
manage than some indoor group housing systems.
The AVMA recognizes that veterinarians approach the issue of pregnant
sow housing from different viewpoints based on personal and societal
values. Some veterinarians are opposed in principle to close
confinement of animals, some are opposed in principle to the use of
animals for food, and some work with the swine industry to maintain
animal health and productivity.
This position statement is based on consideration of animal welfare as
assessed through the scientific literature and professional judgment
and experience. Concerns that commonly arise regarding animal welfare
are that:
- Animals should function well in the sense of being healthy and thriving,
- Animals should feel well, especially by prevention of serious pain, hunger, fear, and other forms of suffering, and
- Animals can live in a manner consistent with the nature of their species.
- Each of these elements needs to be considered when drawing
conclusions about animal welfare. The science of animal welfare
includes assessments of physiology, behavior, production and
health. A review of the literature indicated the following:
- Physiology—Gestation stalls do not induce a physiologic stress
response compared to group housing for pregnant sows.
- Behavior—Sows show different behavior when housed in gestation
stalls as compared to some group pens because of restricted movement,
reduced caloric consumption, reduced opportunities to forage,
absence of bedding, and restricted social
interaction.
- Production—Sows kept in gestation stalls have production performance not different than sows kept in groups.
- Health—The rate of sow injury is reduced in gestation stall
housing compared with group housing. Industry experience
indicates that other aspects of health are predominantly affected
by factors other than the housing system.
The science and professional judgment indicate that we cannot
consider housing systems in isolation from other important factors that
influence animal welfare. These include:
- Management—This by itself is a major determinant of animal
welfare. Some housing systems can be expected to work well at one level
of management, but not at another.
- Feeding system—With concentrated diets, there is a need to limit
feeding to avoid health problems, but this can result in chronic
hunger, restlessness, motivation to forage, and competition for
food. Systems that might work well with one feeding system may
not work well with another.
- Environmental features—Certain environmental features allow sows
to occupy their time and escape from aggressive group mates. How
well a housing system functions may depend on whether such features are
present.
- Type of sow—There are important genetic differences in
temperament that affect how well sows function in different
housing systems. There are also individual differences; a housing
system that is good for more dominant animals may not be
favorable for less dominant ones.
Conclusions:
1. Given the number of variables and large variation
in performance within both group and stall systems for pregnant sows,
no one system is clearly better than others under all conditions
and according to all criteria of animal welfare.
2. Sow housing systems should:
- Minimize aggression and competition among sows;
- Protect sows from detrimental effects associated with environmental extremes, particularly temperature extremes;
- Reduce exposure to hazards that result in injuries, pain, or disease;
- Provide every animal with daily access to appropriate food and water;
- Facilitate observation of individual sow appetite, respiratory
rate, urination and defecation, and reproductive status by
caregivers; and
- Allow sows to express most normal patterns of behavior.
3. All systems have advantages and disadvantages for
welfare. Current group systems allow freedom of movement and social
interaction. However, these same systems, when they fail to work
well, lead to problems, especially in the areas of aggression, injury,
and uneven body condition. When they lack manipulable material, sows in
group systems are also unable to forage. Current stall systems minimize
aggression and injury, reduce competition, allow individual feeding,
and assist in control of body condition. Stalls, however, also
restrict movement, exercise, foraging behavior and social interaction.
Because the advantages and disadvantages of housing systems are
qualitatively different, there is no simple or objective way to rank
systems for "overall" welfare.
4. To address animal welfare in the long term,
advantages of current housing systems should be retained while making
improvements to overcome problems identified. Improvements should be
adopted as soon as:
- The technology is sound enough that producers can adopt it with confidence,
- The skills needed to operate the systems are understood and available, and
- Systems are economically viable.
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