This mobile application, called "Guide Bulls", allows breeders, technicians, inseminators or commercial seeds, to access all bulls marketed or used for AI race Prim'Holstein. It offers the user the possibility to select bulls, particularly through advanced filtering, in order to build a lot, to consult the detail index of a bull, to consult the list of breeders marketed by company, type of seed and price, and access the index history of an animal. The application works in both online and offline modes. The bulls and their indexes are updated automatically.