Because of the fact that this system was developed for dairy cow farmers and animal husbandmen, therefore, the certainty of symptoms occurred from observations of users provided a more precise diagnosis. The diagnosis in this step, system made a question to the user to specify the certainty factor of occurred symptom which the user specified in the disease screening step and also was symptom of possible diseases. After that, system made a question to the user to specify more symptoms which the user did not yet specify.