A really important first step is careful observation by the farm and farm staff to understand which pigs are affected, typically at what age, how many pigs are affected in the batch, what the diarrhea looks like.Is it watery or pasty, does it contain blood or mucus and perhaps what color is it?
It could be black or brown or yellow and really importantly, is it homogenous in consistency or is it kind of chunky? These are all really important features and they help narrow down the cause of the diarrhea. If the correct samples are submitted properly along with a detailed history and knowledge of vaccination and medication status along with the observations from the farm, the rate of diagnosis is actually pretty good.
Swine vets are trained to narrow down the list of potential causes before the samples are submitted which helps to limit the number of tests that are requested and the overall cost. That's why obtaining a history and those features of the diarrhea are so important. Understanding what diseases or pathogens are at the root of the problem also helps to fine tune treatment strategies and improve their effectiveness.
Dr. Harding encourages producers to work with their herd health veterinarian to determine the most relevant information and the best samples to submit.
Source : Farmscape.ca