Abstract
Infections with parasites are worldwide one of the most important factors causing significant economic losses in ruminant production. The increasing resistance of parasites to treatments and concerns over possible chemical residues, enviromnental impact and cost of treatments have led to an increasing interest in genetic selection for resistance to parasites as an alternative or supplement to the use of drugs. Evaluation of breeds within certain species in different breeding situations and environments has proven the possibility of breeding for parasite resistance. This will lead to a decreased number of treatments per animal.