18. The main type of outdoor production system involves paddocks for farrowing sows, in-pig dry sows and service paddocks for weaned sows and boars, usually in weekly groups depending on the herd size. Progeny are normally weaned at about three weeks of age and either moved off the field into permanent buildings or into specialist weaner accommodation set up in the field until they reach 10 to 12 weeks of age. Outdoor finishing systems are rare.
19. Accommodation for weaners usually comprises a monopitch structure with an insulated roof and provision for ventilation, but no floor, and an outside run made from hurdles. A deep straw bed is provided for a group of 30 to 50 weaners. Feed and water are available on an ad lib basis. The hut is moved to a clean site between batches or if conditions in the run become too wet.
20. Many service systems involve mixing sows at various stages. The most common system involves introducing a small number of sows to a group of boars each week for 3-4 weeks. This becomes a stable group during the dry sow period until the pigs are re-mixed with sows of the same stage of pregnancy prior to farrowing.
21. A recent development from Denmark, currently being tried in the UK, is the system of keeping sows in dynamic groups from service. A typical system for a 400 sow herd would involve four dynamic groups of 32 sows and four boars housed in a straw bale structure with a tarpaulin cover and access to the paddock (although there is also the possibility of allowing access to a permanent building). Sows are weaned into a separate paddock where they are fed generously or ad lib for about four days. When they show first signs of oestrus they are transferred into one of the dynamic groups and aggression is not normally a problem because of oestrus and boar activity. Four sows are removed each week when seven to eight weeks in pig and mixed with other sows at the same stage in dry sow paddocks. This system offers better control over service and boar activity. We welcome this, and the further development of individual boar penning and fully controlled service, which help to avoid potential problems to sows and boars from excessive mating.