[Pathogen supply modified by environment and stage of production].

Animal health status depends on the capability of the animals to resist the infection pressure of micro-organisms in the environment. This balance between resistance and infection pressure is very strongly influenced by farm and housing conditions. The infection pressure in the environment of the pigs is greatly reduced by good hygiene in the supply of feed and water, employment of the 'all in - all out' system with effective cleaning and disinfection between groups, and constant air change related to the age and weight of the animals. The resistance of the pigs is favourably influenced by a good vaccination strategy and a comfortable housing climate. Disease outbreaks are clearly reduced in houses with small separated compartments, consistent use of the 'all in-all out' system, and very high standard of climate control directed towards the requirements of the animals in each compartment.