Rather, it is the chief symptom produced by a variety of bacteria, viruses, protozoa, environmental stresses, and feeding errors. No breed of cattle is inherently immune. Beef and dairy calves are equally susceptible. About anything that can be said regarding calf scours is relative to something else or has its exceptions. The incidence and severity of scours are influenced greatly by environmental conditions, e.g., temperature, humidity, draftiness, concentration of animals.
Calves are more susceptible to serious scours at birth than at any other time.
The extreme susceptibility of newborn animals to digestive upsets is due in part to a sterile and nonfunctional state before birth. A calf's digestive tract matures rapidly following birth, but it may be exposed to harmful agents immediately. Every day a calf lives without a diarrhea, there is less chance it will develop serious scours. Animals derive immunity to infectious disease from blood proteins referred to as antibodies or gamma globulins. Some animals, such as people and rabbits, are born with relatively high antibody levels that pass directly into the bloodstream from the mother's blood.