Tolerance and resistance are two different defence mechanisms within the immune system that differ from each other in many ways: However it is not clear which of the two is the most advantageous in dairy production. Resistance is described as the ability to fight a pathogen in a host. Tolerance is, on the other hand, not aggressive to the pathogen per se, but rather protects the host and its tissues. Furthermore tolerance rather offsets the toxin from, for example, a parasite whilst resistance offsets the parasite itself. Resistance is however disease specific, which means breeding for a large number of diseases is needed in order to make resistance worth the cost for the host.