AHOL (Animal Health Ontology for Livestock) is an ontology of characteristics defining health issues of livestock in their environment (EOL) linked to their phenotypes (ATOL). AHOL aims to: - provide a reference ontology of health traits of farm animals for the international scientific and educational - communities, farmers, etc.; - deliver this reference ontology in a language which can be used by computers in order to support database management, semantic analysis and modeling; - represent traits as generic as possible for livestock vertebrates; - make the AHOL ontology as operational as possible and closely related to measurement techniques; - structure the ontology in relation to animal production