Dossier

Group-housing and mixing of sows

Council Directive 2008/120/EC laying down minimum standards for the protection of pigs states that pregnant sows must be housed in groups from four weeks after service until one week before the expected time of farrowing. Mixing of unfamiliar sows leads to agonistic behaviour to establish social relationships, and is therefore a challenge to sow health and welfare. Further challenges for sow welfare are: living in groups associated with competition for limited resources (especially food), lack of satiety due to restrictive feeding of pregnant sows, and climate and climate and resting comfort, in particular on heat stress.

Source photo: © FLI, A. Schubbert

This dossier aims to help Competent Authorities and other stakeholders with issues related to sow group-housing and mixing. The dossier is updated periodically by the EURCAW-Pigs team. The text is meant to support Competent Authorities, and is not legally binding.

Each EURCAW-Pigs dossier addresses the following items: ‘Legislation', ‘Welfare indicators’, ‘Knowledge’, 'Inspiring examples' and 'Training courses'. This dossier is based on EURCAW-Pigs’ “Review on group-housing and mixing of sows” providing knowledge on sow behaviour and their cohabitation in social relationships. Four focus areas for inspections of welfare in sows kept in groups under commercial conditions are highlighted: Mixing of unfamiliar pigs; Competition for resources; Restrictive feeding; and Climatic and resting comfort.

This dossier also addresses examples of group-housing systems for sows after weaning and in early pregnancy, and elaborates on welfare issues resulting from feed restriction and competition over feed in pregnant sows. For this purpose, two specific knowledge sections are added to the dossier. This are based on corresponding reviews developed by EURCAW-Pigs.

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The legal requirements related to group-housing and mixing of sows can be found in Council Directives 98/58/EC on the protection of animals kept for farming purposes, and 2008/120/EC on minimum standards for the protection of pigs. In EURCAW-Pigs' Thematic factsheet on group-housing and mixing of sows, the relevant legal requirements are summarized and presented in conjunction with the four focus areas for inspections.

Directive 2008/120/EC, Article 3(4), states that: “Member states shall ensure that sows and gilts are kept in groups during a period starting from four weeks after the service to one week before the expected time of farrowing. (...).“ Whereas, “(...). By way of derogation from the first subparagraph, sows and gilts raised on holdings with fewer than 10 sows may be kept individually during the period mentioned in that subparagraph, provided that they can turn around easily in their boxes.”

Relevant extracts of the specific requirements are given in EURCAW-Pigs’ “Review on group-housing and mixing of sows”.

_{Source photo:}_{©FLI, A. Schubbert}

Sow welfare during pregnancy increases when group-housing facilities and management practices consider more the behavioural and physiological needs of sows and do not force them to cope with stressful housing environments. For mixing of sows, e.g., research results suggest to use particular mixing pens in which sows should be kept for the first 2-3 days after mixing. These pens should allow the sows to achieve a flight distance of 10-12 m.

Guidance
In EURCAW-Pigs’ Review on group-housing and mixing of sows, suggestions for improved practices are provided for each of the four focus areas to enhance sow welfare when group-housed.

Mixing of unfamiliar animals
Other options to improve the welfare of sows around mixing, besides the use of mixing pens, include, e.g., provision of good quality flooring to prevent slipping and falling, and provision of escape opportunities. Sows should preferably be kept in static groups where they are mixed only once during gestation. Mixing sows at weaning or in the first week after insemination reduces the risk of embryo mortality and therefore smaller litter sizes.

Competition for resources
Reducing competition for resources may be done by, e.g., adequate access to resources in space (no narrow passageways or placement in corners) and time (permanent access to enrichment materials).
Electronic sow feeding, which is a localised resource and does not allow simultaneous feeding, should be positioned away from busy areas and other resources. Lying areas should be separate from the activity and dunging areas, and provide shelter and a view of the surroundings.

Restrictive feeding
The adverse consequences of restrictive feeding (hunger, stereotypies, frustration) may be mitigated by including including more fibre in the diet, allowing a larger volume of food without increasing the energy level and nutrient composition. Fibrous materials can be offered separately in readily accessible racks or on the floor. Providing both fibrous ingredients in the diet and ad libitum access to roughage is the most effective way to increase satiety.

Climatic and resting comfort
Climatic and resting comfort can be improved by clean, dry bedding (e.g. straw) or cushioning, e.g. using rubber mats to improve resting comfort and reduce leg and claw problems. Other measures include proper heat disposition (cooled air, floor cooling, misting and sprinkling systems, etc.), warm and cool surfaces for resting (e.g. a partly-slatted floor), and adjusted management (e.g. feeding and thermal control) during periods of hot weather.

See "Tools for welfare inspection" for a description of welfare indicators, helping to identify welfare issues.

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In 2021, the EU Commission announced it intends to phase out stalls for sows after weaning and in early pregnancy by 2027. The announcement was part of the Commission’s response to the European Citizens’ Initiative “End the Cage Age” launched in 2018. EURCAW-Pigs made a compilation of examples of group-housing systems for sows after weaning and in early pregnancy (see ‘Show more’).

Sows’ needs and risk factors

At the present time, EU regulations still allow sow stalls from weaning until four weeks after service (see Council Directive 2008/120/EC, Article 3, Point 4.). However, in early pregnancy, sows have the same behavioural needs as in late pregnancy. This means sufficient space is required for them to engage in social behaviour as well as safe feeding places and access to comfortable lying places. Alternatives to sow stalls have to allow for sows’ high motivation to express oestrus behaviour, while minimizing risks of injuries and distress. In addition, group-housing systems after weaning until four weeks after service have to provide a protective working environment for stockpersons to perform reproductive measures, such as artificial insemination and pregnancy detection.

The review “Review on alternatives to stalls for sows after weaning and in early pregnancy” addresses important events from weaning, oestrus and implantation in the sow’s reproductive cycle and provides measures to reduce the risks associated with group-housing. The review ends with a compilation of examples of group-housing systems for sows after weaning and in early pregnancy.

Source photo: ©Lene Juul Pedersen

Pregnant sows are generally fed at a restricted level to avoid overweight/high body condition score and the risk of problems at farrowing. However, restrictive feeding has welfare implications as it may lead to hunger, stereotypic behaviour and increased aggression. The causes of and ways to reduce these risks to animal welfare were reviewed (see ‘Show more)’.

The review “Review on hunger induced behaviours: aggression and stereotypies” aims to support inspectors in understanding the science and regulations related to pig welfare concerning hunger induced aggression and stereotypies. Underlying mechanisms and causes of these behaviours in sows related to hunger are described. Furthermore, measures to reduce welfare risks related to aggression and stereotypies are discussed followed by suggestions how to measure these behaviours.

Minimising welfare problems

The review describes several ways to reduce the welfare issues resulting from feed restriction. They divide into possibilities to reduce the underlying problem of hunger and those to mitigate the resulting aggression and stereotypies. To reduce the root cause of the problem, sows need to feel more satiated during gestation which can be achieved by e.g. a higher content of fibre in the diet. Possibilities to mitigate aggression and stereotypies relate to aspects of housing such as space, flooring, substrates, feeding system, and complexity of the environment.

For assessments of stereotypic behaviour and increased aggression, indicator factsheets are developed which can be found in the next section on “Tools for welfare inspection”. Aggression can be measured directly, by observing behaviour, and indirectly, by assessing the resulting skin lesions.

Source photo: ©FLI

In commercial housing, pregnant sows are fed restricted with one or two meals per day to prevent excessive weight gain in pregnancy, which may cause problems around farrowing. However, restrictively fed sows are often not satiated and still show a high feeding motivation, which is a sign of hunger and may provoke stereotypies. Thus, pregnant sows and gilts must be given a sufficient quantity of bulky or high-fibre food in addition to a high-energy food in order to satisfy their hunger and given their need to chew.

In the short review “Enrichment materials for sows during pregnancy” EURCAW-Pigs provides a background on the behavioural needs of sows in terms of feeding and exploring. Furthermore, different methods to offer enrichment material to sows during pregnancy are highlighted.

Foraging motivation

Feed intake is accomplished with foraging performed by sows for 40-70 % of the day in semi-natural environments. Pigs perform exploratory behaviour also at objects of the housing environment (e.g. chains) even when a biological stimulus (e.g. organic substrate or food) is absent. This indicates that exploratory behaviour is also intrinsically motivated. According to EU legislation, sows must have permanent access “to a sufficient quantity of material to enable proper investigation and manipulation activities, such as straw, hay, wood, sawdust, mushroom compost, peat or a mixture of such, which does not compromise the health of the animals” [Article 3(5) and Annex I, Chapter I, Point 4].

Substrate-based enrichment recommended

For feed-restricted sows, substrate-based enrichment (in the form of roughages) is recommended, since it not only provides exploration opportunities but also contributes to satiety and reduced prevalence of stomach ulcers. High amounts of roughages are best provided in housing systems with solid floors. For slatted floor systems, further investigations are needed to develop object-based enrichment materials that include characteristics such as the possibility to root.

Intro photo: (©Antje Schubbert, FLI)

Welfare indicators can be used to monitor the welfare of group-housed sows. For four key areas to focus on during inspections, EURCAW-Pigs identified relevant indicators to assess the welfare of pigs. Each indicator is described in an indicator factsheet, by suggesting an inspection and scoring method, and summarizing the underlying welfare concern and legal requirements. See 'Show more' for all indicator factsheets.

Assessment of welfare of sows

Indicators to assess the effects of mixing:

Skin lesions (also “Competition for resources”): Lesions include broken skin, fresh wounds and healing lesions. Skin lesions can result from aggression related to establishing a social relationship with unfamiliar sows and/or competition for resources.
Lameness (also: (also “Climatic and resting comfort”): When lame, a pig is unable to use one or more limbs in a normal manner. Lame pigs experience pain and discomfort. Causes: agonistic interactions on slippery floors, but also prolonged lying duration on hard floors.

Indicators related to competition for resources are:

Vulva lesions: Damage to the vulva may indicate competition for food, e.g., when sows are feeding in stalls and are being approached from behind by a competitor/biting.
Body condition: Body condition indicates whether individual sows have obtained
sufficient food.
Manure on the body (also “Climatic and resting comfort”): Sows may be dirty from manure on the body due to e.g., lack of (lying) space, thermal stress or bad ventilation.

Indicators related to restrictive feeding are:

Stereotypies: Behavioural patterns performed repetitively in a fixed order and without any apparent function (e.g., sham chewing, tongue rolling, bar biting). They may be a sign of frustration due to hunger and inappropriate foraging behaviour.

Indicators for climatic and resting comfort include:

Panting: Sows try to lose heat by highfrequent, open-mouth breathing.

_{Source photo:}_{©FLI, A. Schubbert}

For good practices implementing EU legislation on-farm, inspiring examples and demonstrators are identified. The examples of commercial farms given here address some good practices regarding group-housing and mixing of sows. Demonstration of good practices are excellent ways and proven methods of dissemination of knowledge, exchanging ideas, harmonizing assessments, and changing attitudes. Disclaimer: This is not an endorsement.

Mixing pens

Standard group-housing systems may not provide sufficient space at the time of mixing. Consequently, several authors suggest to use particular mixing pens in which sows should be kept for the first 2-3 days after mixing. These pens should:

Allow the sows to achieve a flight distance of 10-12 m.
Include straw or rice hulls as bedding providing both rooting material and a good grip for the claws while fighting or fleeing.
Include visual barriers to allow sows avoiding fights by hiding from dominant sows. Barriers may reduce total aggression by nearly 30 % in the 12 h after mixing.

Provision of roughage

Roughage, provided as feedstuff, should always be offered in racks or (automatically) in troughs. A rack for pregnant sows:

Is suitable when having a feeding height of 40-45 cm and when the distance between bars (axial dimension) is 11-13 cm in order to allow ready access to the roughage.
Can be placed in the outdoor run if available.
Should be placed in a position allowing access for all sows and, thus, avoiding that roughage becomes a limited resource.

Rubber mats

Rubber mats are a suitable alternative for straw bedding to offer a comfortable lying area for pregnant sows:

Soft rubber mats improve lying comfort considerably compared to concrete floors.
Lying times and frequency of lying in half-recumbent position increase compared to sternal lying.
The prevalence of limb lesions and the risk for lameness can be reduced.

Inspiring video: Fibre rich food

Restrictive feeding - Vision Pig: In this short video, Jan-Hendrik Hohls, a German Farmer, states that the best material to enrich sows is the food itself. Especially dietary fibre rich food keeps sows busy with food intake for 4h per day. This promotes calmness in the group and avoids negative social interaction. Feeding rich dietary fibres ration needs a manure systems that can deal with it. That’s why Jan-Hendrik Hohls uses a mechanical manure system underneath the slats. Disclaimer: This is not an endorsement.

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Aus dem Themenblock "Sauenhaltung": Zufriedene und ruhige Sauen - das Futter als wichtiger Faktor

Vision Pig - MuD Tierschutz

In collaboration with national training bodies and national reference centers on animal welfare, EURCAW-Pigs develops training guides for the different welfare topics as standards for national training in EU Member States.

Learning goals

On the subject group-housing and mixing of sows:

A brief history of legislation on sow group-housing and mixing including but not limited to stall dimensions, group house period, enrichment, group space allowance.
Knowledge about the intention of the EU legislation (e.g. why should sows be kept in groups?)
Knowledge about the reproductive cycle of the sow and updated knowledge on behavioural and physiological needs of sows during oestrus and gestation.
Updated knowledge about the social structure and social behaviour of pigs as well as the biological background (will include for example: The difference between rank order fighting and competition for access to resources; How to prevent damaging behaviour like vulva biting).
Knowledge about indicators suggested by EURCAW to use to check compliance within the main risk areas and the strength/weaknesses of these. Tools for calibration and practical training in calibration using the EURCAW indicators.
Knowledge about initiatives to end stall housing completely (i.e. ‘End the cage age’), risk of stress during early pregnancy including remedial actions drawing on examples from Sweden and the UK.
Knowledge about challenges in relation to communication with farmers during inspection.

Inspection-driven welfare improvement

Additionally, EURCAW-Pigs provides examples of training plans and materials used in different Member States in English, to the extent possible, and training suggestions for improvement of communication skills and ways to support inspection-driven welfare improvement. This is presented on the training overview page.