Design requirements

Pens - Allow 2.7-2.8 sq.m. per sow for lying and defecating. Do not house groups of sows in long narrow pens. These will increase the incidence of vulva biting.

Yards - Allow 3.4 sq.m. per sow. At the recommended stocking density there is a marked reduction in fighting episodes when sows are mixed.

Floors and bedding - Solid concrete floors bedded with straw or other suitable materials are best. Totally slatted floors are not recommended due to the high levels of lameness, arthritis and the foot problems that occur.

Solid floors can be bedded with a minimum amount of straw but in all cases the floors should be well insulated. If minimum amounts of straw are to be used the floors should be laid on a 1:20 slope so that the straw bedding is walked "towards the defecating area". Solid defecating areas should be well drained and the manure removed three times weekly.

Water - This should be provided ideally by a self levelling small trough or one bite drinker per 15 sows.

Feeding - This can be provided by feeders suspended above the lying area and the feed dropped to the floor (dump feeders) or alternatively a single feeder that spins the feed out across the lying area. Wet feeding systems are also being used successfully feeding the sows from troughs placed down the sides of large straw yards or along the front of the pens. Electronic sow feeder systems (ESF) are common. Here the sow is individually fed a maximum daily amount when it enters the feeder station in response to a transponder placed in the ear or around the neck. One feeder station will accommodate 20 to 30 sows. Trickle feeder systems have been developed whereby the feed is dispersed in small amounts at a time, sufficient to keep the sow feeding continuously. The troughs are divided by short divisions to separate each animal during feeding. They are suitable for groups of up to 12 sows.

Group size - This should ideally be no more than 30 sows per pen, unless electronic sow feeders are used when the size may be increased. Some farmers keep up to 150 sows in a dynamic group but this is not recommended because with an increasing number of sows there is a tendency for more welfare problems to occur. In spite of this the recently introduced Danish Dynamic Mating System, which has group sizes of up to 80, works very well if the stockmanship is good. Small numbers of sows are introduced into the group weekly when they are on heat and are less aggressive and they are naturally mated by the boar.

Temperature requirement - This depends on the amount of bedding and floor insulation and ranges from 16 to 20ºC (61 to 68ºF).

Management, welfare and disease

Welfare problems and disease arise due to the aggressive nature of sows in group housed systems. Furthermore this aggression creates problems of varied feed intake and predisposes the individual under-nourished sow to disease.

The ideal management system should allow newly weaned sows to mix in a large pen together with a boar for the first four days. He should be then removed and the sows held in stalls for a period of 48 hours over the mating period after which they are returned to the group. The boar is introduced again for the next 21 days. Sows should be maintained in the same group throughout the whole of pregnancy. Alternatively, the sows can be weaned into stalls mated in boar pens and kept in stalls or cubicles for the first half of pregnancy before being group-housed. If pregnant animals are mixed together between 2-21 days post-service there is a risk of higher embryo mortality and more variable litter size. Wet feeding ESF and trickle feeding systems give a more even feed intake compared to group feeding systems. If aggression is a problem, particularly when sows are mixed, a series of soft rubber mats (1.2m x 1.2m) suspended vertically, 500mm above the floor, over the lying area in large pens provides a means of separating one sow from another when a fighting episode commences.

Sows fed in electronic feeders have the advantage of individual feeding but aggressive behavioural patterns can develop, particularly when they are waiting to enter the feeders. This can cause considerable stress particularly to animals that have just joined a large group. Severe bullying with trauma and skin damage can take place and poor hygienic conditions and wet areas often develop around the feeder stations.

ESF systems require careful design and skilled experienced stockmanship. It is best to use feeders with a separate front or side exit door so that sows do not back out and be confronted by sows which are eager to feed. Some sows tend to lie in the feeder thus blocking others. If the design of the layout is not well thought out and the stockperson not properly trained there may be an unacceptably high level of vulva biting and badly scratched and bruised skin.

If you decide to construct an ESF system you should first visit and study successful established ones and get competent training in ESF management. Training gilts to ESF systems is necessary.

If possible the stockperson working the system should be involved in the selecting of the equipment and the design of the yards. He should be enthusiastic, committed to making the system work and should understand the computer technology. He should be competent to undertake every day maintenance. In areas of frequent power failure, a standby generator will be necessary.