Under the previous Animal Welfare and Livestock Husbandry Ordinance (TierSchNutztV), the restraint of sows in the mating centre – and thus the individual housing of the animals – was permitted from weaning until a maximum of four weeks after mating. Following the amendment of the TierSchNutztV in February 2021, sows must – after a transition period of eight years – be provided with 5 m² of space during the period between weaning and mating, and group housing must be made available. Restraint is permitted solely for the purposes of oestrus detection, the insemination process or medical treatment. Due to the high space requirements in the mating centre, some farmers will likely reduce the duration of housing in this phase in future. Consequently, oestrus detection, the mating of sows in oestrus and pregnancy checks will be partially relocated to the waiting area.¹ Almost all sow-rearing farms are therefore currently faced with the decision of whether and how to make their mating area fit for the future. No later than three years after the amendment to the Animal Welfare (Livestock) Ordinance comes into force, farmers must submit an operational and conversion plan for the mating area if they intend to continue sow rearing in the future. Farmers who wish to cease sow rearing must make a binding declaration to the authorities and cease sow rearing five years after the amendment comes into force (February 2026).
As part of the MuD project ‘Improvement and Enrichment of the Housing Environment for Pregnant Sows’ and the project ‘Testing and Evaluation of New Housing Methods for Sows in the Mating Centre’, experience has been gathered on various farms regarding the construction and conversion of mating centres, which is intended to support farmers in their decision-making.
 

When sows are grouped together after weaning, fights often break out, some of which can be quite fierce. These fights serve to establish a hierarchy and may be intensified by oestrus behaviour.⁴ An arena pen is a suitable solution for minimising the risk of injury during fights. This allows the sows to engage in their ranking battles in a suitable housing environment before oestrus and mating.⁵ From the 3rd to the 8th day after weaning, the sows come into oestrus and can be mated. Subsequently, between the 11th and 21st day, the embryos implant in the uterus. During this critical phase, stress and agitation among the animals should be avoided, as fertilised eggs can die off particularly quickly. Therefore, the establishment of the hierarchy should take place immediately after weaning. The animals should then be moved to the waiting pen either shortly after mating or four weeks later.¹
If sufficient space is available, the mating centre is also suitable as an arena. 5 m² per animal must be provided in this area. Certain requirements should be observed: the floor of an arena should be dry and non-slip to minimise the risk of injury. A flat, solid floor is preferable, as it is gentler on the hooves. Resting areas must be designed in such a way that they remain dry and clean. This can be influenced by the provision of resting stalls, lighting, air circulation, floor design and other factors. One way to minimise the risk of injury is to use a light layer of straw to cover any sharp edges on the floor.² In the arena, the animals should have sufficient opportunities to move away and retreat, as well as space and bedding, ideally deep litter. Well-placed, relatively short privacy screens with an escape route or an additional second exit to the outdoor run can serve as an alternative, if such a run is available on the farm. Ideally, the arena should be round and free of corners where lower-ranking animals could become trapped. However, this is usually not feasible from a structural point of view. Therefore, a living area for the animals that is as square as possible should be selected. The aisle width should be at least 3 metres to allow the animals to avoid each other.² The pen should be thoroughly inspected, and objects with which the animals could injure themselves should be avoided. Nipple drinkers, for example, should only be used with a protective guard to minimise the risk of injury at the drinkers. If there is insufficient space for an arena, a mobile arena can be created using plastic panels on castors. As a rule, just a few hours to a day is usually sufficient for the hierarchy to form.² However, the smaller the differences in the animals’ strength, the longer the process takes. Should further aggression occur subsequently, this must be kept to a minimum. Measures include, for example, providing additional feeding stations for grouping, offering straw and roughage, and immediately separating sows that display aggressive behaviour.⁶

The actual amount of space that is best for sows in group housing at the breeding centre depends on the conditions of the respective farm. It depends on whether an arena is available to the sows, whether the animals are kept on deep litter or slatted floors, and how slip-resistant the floors are. However, the minimum area in the arena should be 5 m².⁷ Another factor that should not be underestimated is the behaviour of individual animals during oestrus.
 

There are virtually no limits to group size in the mating centre; however, the conditions in the subsequent waiting pen must be taken into account. The sows can be moved there after mating, unless a combined mating/waiting pen is already in use. When forming the final groups in the waiting pen, it is advantageous not to introduce any unfamiliar animals to increase the group size. Where possible, therefore, the group should only be reduced in size after relocation. Due to their physical condition, gilts should be housed separately from sows until their first farrowing. The differences between the requirements in the mating and waiting pens have been aligned, so that the mating pen can also be used as a waiting pen, depending on the farm.⁷ However, sufficient space for each animal in the mating centre must be taken into account. To ensure that sows in group housing can find sufficient rest, opportunities for retreat should be provided. This can be achieved, for example, through privacy screens, outdoor runs, clearly separated pen areas or even straw bales.
⁶
 

According to the Animal Welfare Ordinance (TierSchNutztV), farrowing crates must be reopened immediately after insemination, which reduces stress in sows.³   Various methods for restraining sows during insemination are listed in Table 1.

The restructuring of sow housing is intended to improve animal welfare. The sows have more space, can move around freely and express their social behaviour. However, a drawback is that the animals suffer increased physical injuries, such as skin lesions or lameness, as a result of social contact.¹ Most injuries occur during the oestrus period and the establishment of the hierarchy. Skin injuries to the shoulder region and back usually occur during rank-fighting. After oestrus, however, most injuries are found on the flanks, hindquarters and back.¹ It should be noted that deep scratches, open sores or bloody wounds resulting from social interactions occur only to a limited extent. Most skin injuries caused by other pigs are relatively minor.³
Due to group activity, such as pigs jumping on one another, increased lameness is also possible at the start of group housing.¹⁰ A calm group and good housing conditions, such as optimal flooring with deep litter or flat, reinforced surfaces covered with litter, can minimise this.¹ When using slatted floors, care of the hind feet must be intensified. Experience from Scandinavian countries shows that stress on the sensitive feet can really only be reduced on deep litter.¹¹ In the LSZ Boxberg project, there was no difference in lameness between animals that were restrained for five days and those that were not, although one might assume that restrained animals would spare their musculoskeletal system more than unrestrained animals. As early as after five days, the noticeable lameness in the animals subsides on its own, as the results from the LSZ Boxberg show.³   If injured or sick animals need to be removed from the group and housed in a sick pen, visual and olfactory contact with the group should be maintained to avoid renewed agitation after they are returned to the herd.

A practical recommendation is to provide sick pens for 5% of the animals kept in groups. These should measure 5 m². It is important to observe the animals closely during daily checks and, above all, during the heat period, and to separate any injured animals immediately so that minor injuries can heal quickly and the number of sows with foot and leg problems does not increase as a result of free-range housing.

Anyone planning to build a new breeding centre or renovate an existing one should not overlook the installation of cooling facilities: these must be provided in accordance with the implementation guidelines of the TierSchNutztV. The design of these cooling facilities naturally depends heavily on the specific on-site conditions of each individual farm. In new buildings, ground-source heat exchangers can be an effective way of regulating the temperature of the supply air in both summer and winter. Floor cooling, CoolPads, misting systems and (micro) wallows can also be retrofitted into existing barns with varying degrees of effort. When using evaporative cooling systems in enclosed barns, attention must also be paid to humidity levels.

The amendment to the Animal Husbandry Ordinance imposes entirely new requirements on housing systems. As a result of the significantly increased space requirements, construction costs are also rising considerably. Experience shows that a new building is not necessarily required to meet future standards for sows. There are various ways to make existing buildings fit for the future. With good management, production performance can remain consistent.⁵