The AHOL ontology (Animal Health Ontology for Livestock) was built collaboratively within a network of experts in the livestock health field, in order to describe production diseases. Its structure is based on the type of disease: communicable, non communicable, genetic, metabolic, physical or psychological. The properties of each disease are related to associated symptoms (the expression of a phenotypical character), the affected organism (livestock, poultry, mammals, fishes) or the one causing the disease (virus, bacteria, fungus, parasite).