This is one of the most serious problems facing young dairy cows because it is usually systemic in a nature and is difficult and expensive to treat. This condition can usually be linked back to inadequate colostrum intake in addition to unsanitary birthing conditions. Sites of bacterial entry are often the umbilicus, wounds, nose and mouth. Early signs are weakness, lethargy, lack of suckling and can sometimes lead to other complications.
Diarrhea can often be interpreted as a lax disease, but in some cases, especially when talking about neonate calves, this disease can cause serious medical problems or even death. Diarrhea leads to dehydration as well as electrolyte and acid/base imbalances. Diarrhea can be viral, bacterial, fungal, or nutritional in nature, and management of primary infection is necessary for sound treatment.
Pneumonia is a serious disease that can progress quickly and ultimately lead to death of calves. Most of the factors that "help" a calf get pneumonia are management issues. Proper cleanliness of pens, ventilation, adequate colostrum intake, and the correct means of shelter all work to prevent illness. If calves are housed together then disease will spread quickly and much more will need to be done to treat the herd. If caught soon enough, pneumonia can be treated successfully with antibiotics and fluid therapy.