Transferring expertise from highly qualified experts to non-expert veterinarians and animal breeders is one of the Central Laboratory for Agricultural Expert Systems (CLAES) main objectives. CLAES used the knowledge based system technology to achieve this objective. Five animal knowledge based systems have been developed for diagnosis animal diseases and/or management farm. This paper presents the different methodologies used to develop these systems in Egypt. The used methodologies are: the hierarchical classification generic task, the case based reasoning and the commonKADS.