It is a common experience for calf raisers: a calf is born that seems to be healthy and strong, yet develops scours within the first five days of life. Although you may think you overfed milk or milk replacer to the calf, this is a common misunderstanding, says Canadian veterinarian Roger Thomson. Calves are much more likely to scour because they have been exposed to an infectious organism.

Where do they get exposed? If a calf becomes sick in the first five days of life, infection most likely happened in the maternity pen, Thomson explains. If calves become sick after seven days of age, they were likely exposed to infection in their own environment — that is, the calf pen.