Like many animals, pigs establish a hierarchical social order when mixed together. When sows are in groups, dominant sows tend to act aggressively (e.g., by biting); they can cause serious injuries to less-dominant sows. Submissive sows also may have difficulty getting access to enough food, which can lead to poor weight gain and pregnancy complications. Gestation stalls were introduced in the 1960s to help protect and nurture all sows during pregnancy. 

The transition to individual stall-style barns happened over a few decades and after considerable investments of time, scientific research and capital by farming organizations. Studies have been conducted that compare the well-being of sows in gestation stalls (sometimes known as gestation crates) with sows housed in groups.

Advantages of individual and group housing

In individual housing systems, sows are housed in a structure large enough for one sow, though the design varies. The advantages of individual housing systems are that they minimize sow aggression and injury, reduce competition, allow individual feeding and nutritional management, help maximize each sow’s body condition and reduce worker injuries; however, they also restrict behavioral expression, freedom of movement and exercise.  In group sow housing, sows move about more freely, but it can be very challenging to ensure each sow receives the proper nutrition and care and is free of injury from more aggressive sows.

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