Typical sow lifecycle in low-welfare conventional sow farm systems

In the U.S., an estimated 6 million sows, or mother pigs, are bred each year to produce litters of market/meat pigs, resulting in hundreds of millions of pounds of pork meat.  

In low-welfare conventional operations, the continuous cycle of confinement is the norm. Most sows will have approximately two litters each year and will give birth to an average of 3.5-4.5 litters in their lifetime. In these conventional operations, the intensive confinement equates to 72.5-77% of a sow's lifetime. 

Breeding & gestation of sows

In standard U.S. operations, the first stage of a sow’s production cycle starts with breeding.

Sows may be bred naturally with a boar; however, artificial insemination is more common.  

How gestation crates affect sow welfare

The typical gestation (pregnancy) for sows is about 114 days – or three months, three weeks, three days. In conventional operations, ~58% of U.S. sows will spend their entire pregnancy confined to a gestation crate. 

Gestation crates are one of the most extreme examples of physical confinement for farm animals today. Gestation crates are typically 7 ft x 2 ft narrow pens made of metal bars providing only 14 ft2 of space for a sow. Each crate is only slightly larger than the body of a sow. Inside the gestation crate, a sow is unable to turn around, walk, or fully extend her legs. At the front of the crate is a feeder and drinker, but otherwise the crate is barren. There is no bedding or enrichment as the floor under the crate is fully slatted to allow their excrement to collect below in a pit. There is no bedding as the floor under the crate is fully slatted to allow the sow’s excrement to collect below in a pit.  

The severe physical restriction of gestation crates leads to numerous health issues for breeding sows, including lameness, pressure wounds, and diminished muscle strength and bone density.

Pigs are highly motivated to forage and will spend ~50% of their day foraging under free-range conditions. Crates hinder the performance of a sow’s innate natural behaviors, including walking, foraging, and rooting. Sows are gregarious social animals, but the constant crating also prevents them from interacting with other pigs. Long periods spent in gestation crates can cause the sows to become severely stressed and exhibit stereotypic behaviors, including bar biting, head weaving, and sham chewing. These abnormal and repetitive behaviors are associated with clinical depression, frustration, and low welfare production systems.  

Productive sows will spend several years in the cages...But as the sows get larger over the years, some cannot fit in the cages and are either slaughtered or forced to live in conditions where they can sleep only on their chests, rather than their sides as they do normally.

Dr. Temple Grandin 

Farrowing & nursing sows

Shortly before she gives birth, the sow is moved to a farrowing crate where she gives birth (farrows) and nurses her piglets for approximately 3 weeks. In the U.S., sows give birth to an average of 12-14 piglets, with each piglet typically weighing two to three pounds. 

How farrowing crates affect sow welfare 

Farrowing crates, like gestation crates, severely restrict a sow’s movement and her natural behaviors. The total farrowing area measures 8 ft by 5 ft, with the sow confined in a smaller individual crate about the same size as a gestation crate (7 ft x 2 ft). This leaves the sow with barely enough space (14 ft2) to stand up, lie down, and nurse her piglets.

Like gestation crates, farrowing crates have a drinker and feeder near the sow’s head, but there is no bedding, and the floor is fully slatted, allowing excrement to fall into manure pits beneath the floor.

Farrowing crates first gained popularity in the 1960s due to concerns about piglet-crushing. However, these highly restrictive systems significantly compromise sow welfare and have many disadvantages for piglet welfare during lactation. 

In the 24 hours before farrowing, a sow is naturally driven to isolate herself from other pigs and gather materials to build a protected nest for her piglets. However, the farrowing crate severely inhibits the sow’s movement, and she is prevented from performing her instinctive maternal behaviors. Research has shown sows kept in farrowing crates are unable to nest build, causing the sows to experience longer farrowing times, and have poorer nursing abilities, more stillbirths, and lighter piglets.   

In a farrowing crate, a sow cannot However, the farrowing crate severely inhibits the sow’s movement, and she is prevented from performing her instinctive maternal behaviors, including fully interacting with her piglets, leaving her frustrated and restless.

Frustrated sows in farrowing crates can develop stereotypic behaviors, like bar biting and snout pressing, like sows confined in gestation crates. 

Photo credits: Gabriela Penela, Jo-Anne Mc Arthur, Andrew Skowron/We Animals Media