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What are the animal welfare issues with mating stalls for pigs?

Sow stall

A mating stall is a crate used to hold a female pig for artificial insemination. In a mating stall, a female breeding pig is able to stand up or lie down but unable to turn around. It is effectively the same as a sow stall, in which a female pig was traditionally mated (impregnated) and then housed during her pregnancy. Current pig industry practice allows the mating stall to confine a female pig for up to five days post insemination. The RSPCA believes that mating stalls should only be used for the minimum period required to carry out the artificial insemination procedure.

Breeding pigs

Pigs farmed for meat are the offspring of the breeding animals in a pig herd. These animals include gilts, sows and boars. As part of the pig production process, gilts and sows are mated to produce a litter of piglets. These piglets are raised to a specified weight and then slaughtered to produce pork and pork products for human consumption, including fresh pork, ham, and bacon.

Gilt = a young female breeder pig who has not yet given birth to a litter of piglets.
Sow = a female breeder pig who has given birth to at least one litter of piglets.
Boar = a male breeder pig.

Gilts and sows are mated either through natural mating (using a boar) or through artificial insemination. Boars are used for the collection of semen for artificial insemination. Boars are also used to bring the gilt/sow onto heat (the time when the gilt/sow is receptive to being mated) as well as to determine if the gilt/sow is on heat and ready to be mated.

Boars reach puberty at around 5-7 months of age. Gilts are considered sexually mature when they are on heat for two days and their oestrus cycle occurs in regular 21-day intervals. Gilts are usually mated for the first time at 6-8 months of age at their second or third oestrus cycle. Sows are on heat for around three days and are usually mated at their first oestrus, about 4-7 days after her piglets have been weaned. If the gilt/sow is not pregnant, she will return to oestrus about three weeks post mating. Pregnancy lasts for approximately 116 days during which time the gilt/sow will be housed in a sow stall (for a period up to six weeks) and/or housed in groups with other pregnant pigs.

Approximately one week before farrowing (giving birth) the pregnant gilt/sow is moved to farrowing accommodation, usually a farrowing crate, where she remains until her piglets are weaned at 3-5 weeks of age. The breeding cycle then starts again.

Mating accommodation

Artificial insemination is the most common mating method used, particularly in intensive indoor systems where the gilt/sow is locked in a mating stall for insemination and may remain confined for up to five days after mating before being returned to group housing.

In systems where pregnant gilts/sows are housed in sow stalls for part of their pregnancy (maximum six weeks), artificial insemination takes place in the sow stall. In semi-outdoor and outdoor systems, gilts/sows are usually brought into larger mating pens for natural mating or artificial insemination and then released back into their shed or paddock, or, alternatively, a boar may join a group of gilt/sows in their paddock. In indoor housing systems, gilts/sows are usually housed in large sheds in groups, whereas boars are housed in individual pens or stalls. In semi-outdoor and outdoor systems, gilts/sows are kept in group paddocks, and boars are kept in a separate paddock or with the gilts/sows. Farrowing accommodation in intensive indoor systems usually consists of farrowing crates, whereas in outdoor systems a gilt/sow is housed in a farrowing hut.

Mating stall

A mating stall is a crate in which the gilt/sow is able to stand up or lie down but unable to turn around. It is effectively the same as a sow stall in which the gilt/sow was traditionally mated and then housed during her pregnancy.

Mating stalls aim to protect gilts/sows from aggressive encounters with other gilts/sows, which may occur when they are mixed into groups after weaning or immediately after insemination. Aggression in recently inseminated gilts/sows induces stress which can affect the hormones secreted at the time that the embryo is attaching to the uterine wall (called ‘implantation’) potentially resulting in pregnancy failure. A key factor to reproductive success is minimising aggression.

Animal welfare issues with stalls, including mating stalls

Pigs are intelligent and social animals, with a complex range of behaviours and needs. When confined to a stall or crate, a gilt/sow is unable to perform natural and motivated behaviours, such as foraging, or interacting socially with other pigs. As a result, gilts/sows in stalls can show higher incidences of aggressive behaviours and abnormal behaviours, such as stereotypies (e.g., repetitive bar biting). These behaviours are considered to occur when pigs are attempting to cope in an inappropriate environment and are indicative of poor animal welfare outcomes.

Key animal welfare concerns:

  • movement restriction: gilts/sows spend 12% of their active time in locomotion but walking, running and turning around is not possible in a stall; the limited ability to get up and lie down in a stall results in gilts/sows lying down more often and for longer as well as changing lying position more often due to discomfort which affects fitness, can result in lameness, and foot injury when the foot gets caught in the slats;
  • insufficient rest/sleep: stalls restrict ability to get up, lie down and adopt a comfortable lying posture, likely disrupting the amount and quality of sleep; difficulty lying down and resting/sleeping in a comfortable lying posture results in discomfort, tiredness and/or frustration (sternal lying results in 10-20% of body surface being in contact with the floor, putting strain on those body parts; lateral lying is more comfortable for pigs); uncomfortable (concrete) flooring with lack of bedding results in sustained pressure on bony parts of the limbs;
  • stress: when on heat, gilts/sows are very active and motivated to have social contact which is restricted in a stall; the stall also prevents a dominance hierarchy from being established and can result in intense aggression (for at least three days) between neighbouring gilts/sows, in contrast to group housing where it is usually resolved within two days; proximity and visual contact means gilts or younger sows feel intimidated because they can’t hide or move away from perceived threats such as older sows in a neighbouring stall;
  • inability to perform exploratory or foraging behaviour: exploratory, foraging, rooting, and sniffing behaviour is practically impossible in a stall; there is a likelihood of redirected oral behaviour (e.g. nosing, licking, biting) towards stall fixtures, floor or trough; these can develop into stereotypies;
  • hunger: gilts/sows are usually on a restricted diet which means they are hungry most of the time; this means that gilts/sows are more motivated to forage for food, however foraging behaviour is restricted in a stall.

Are mating stalls necessary?

The Australian pork industry’s quality assurance program (APIQ) requires that suppliers of a large retailer limit the use of mating stalls to a period up to 24 hours (see APIQ standard p42) suggesting that many pig producers are able to manage artificial insemination of gilts/sows in mating pens, in groups, or with very limited use of mating stalls.

What is the RSPCA’s view?

The RSPCA believes that mating stalls should only be used for the minimum period required to carry out the artificial insemination procedure and that, immediately following mating, gilts/sows should be allowed to return to their group housing. The practice of confining a gilt/sow to a mating stall for up to five days should be phased out.

Where used, the mating stall should have appropriate, non-slip flooring that avoids the risk of foot or leg injury or discomfort. Vertical bars in a mating stall may provide protection from aggression from a neighbouring gilt/sow, however unfamiliar gilts/sows should preferably not be placed next to each other. Aggression resulting from hunger and motivation to forage for food, can be mitigated by increasing dietary fibre. Following mating, gilts/sows should be housed in groups.

Source information

EFSA Panel on Animal Health and Welfare. (2022). Scientific Opinion on the welfare of pigs on farm. EFSA Journal, 20(8), 7421.

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Updated on January 30, 2023
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