In general, pigs in outdoor units have high health status due to low stocking density and reduced infectious challenge. Whilst treatment may be more difficult outdoors, one advantage of this method of pig-keeping is that infection dilution occurs in the open air and lower stocking densities and stress levels tend to keep the animals in better condition: so outdoor pigs are generally healthier than those kept indoors.
However, where disease occurs the implications for outdoor units are serious due to the difficulty in isolating the pig and administering treatment. Prevention is always better than cure and the advice given by the Pig Welfare Advisory Group is that a preventive health programme should be drawn up in conjunction with a veterinary surgeon and incorporating a vaccination, an anthelmintic programme and effective control of external parasites which cause disease.
Any disease can cause welfare problems and stockmen should be aware of this and take preventive action where possible. This may be achieved using routine vaccination programmes. Whilst many diseases may be controlled by vaccination, routine protection against E. coli, swine erysipelas, clostridial diseases and porcine parvovirus should be seriously considered. Outdoor pigs are still susceptible to the usual range of pig diseases and therefore constant vigilance and prompt action is essential. Veterinary assistance should be sought if the stockman’s immediate action is not effective.
In order to maintain herd health it is important to start with high health status stock and to isolate them, as far as practicable, from other herds. Stockmen must be on the lookout for injury, disease and contamination of the site by birds and wild animals and treat the pigs as soon as symptoms occur.
Separate inspection/isolation facilities should be available and can be achieved by the use of electric fencing to isolate a small area which includes a well-bedded, draught-free hut. It is accepted that problems due to re-mixing after a period of separation may preclude this option. Nonetheless, it may be necessary to isolate a sick animal particularly if it is being bullied by its companions.
It is important to monitor the health of boars and to deal quickly with any deterioration whilst the animals are still within their social group. This is particularly the case if a boar is lame, because activity in the service paddock could exacerbate the problem. Should a boar not respond to treatment whilst in the group it should be removed although there are likely to be difficulties in re-introducing the animal. This emphasises the need for early treatment whilst still in the group.
Systems that use groups of boars in service paddocks increase the risk of injury through continuous contact with sows, especially those on heat. This is reflected in higher ratios of boars to sows and higher culling rates. For these systems boars selected for their robustness should be used.
Systems that allow individual housing of boars and supervised services reduce the risk of injury and allow boars to be used of a higher genetic potential, more suitable for the market requirements.