Breeding for sheep parasite resistance in extensive production systems in Uruguay:From phenotype to genotype.

ABSTRACT.- Gastrointestinal parasites (GIP) are one of the main causes of economic losses for sheep farmers worldwide. The need for alternative control measures comes from increasingly critical anthelmintic resistance. One alternative is to include genetic resistance to GIP in breeding programmes, by selecting for worm faecal egg count (FEC). Using this selection criterion since 1994, Uruguay has included genetic resistance to GIP in the genetic evaluation of Australian Merino and Corriedale breeds.