Pigs are medicated continuously for periods of up to 12 weeks during the critical periods of exposure to disease. Dose levels are usually lower than those used for treatment. Fig.4-1 lists the in-feed levels that can be used for the various respiratory diseases.

Continuous medication can be expensive but in permanently populated houses with mixed ages of pigs it can work well with considerable growth enhancement which helps offset the cost.

There is continual suppression of organisms. In severe endemic disease the system can break down. There may also be problems with withdrawal periods in finishing pigs. Continuous medication should therefore be regarded as a last resort. Always ask three questions if continuous medication is necessary:

• Why is there a problem?
• What has gone wrong with the management?
• CAN THIS BE CORRECTED?