Diarrhea in calves less than 30 days of age is caused by a variety of agents. The most common pathogens found in calves are parasites (cryptosporidia), viruses (rotavirus, coronavirus) and bacteria (Salmonella, K99 E. coli and attaching and effacing E. coli or AEEC), says Pat Blanchard, veterinarian with the California Animal Health and Food Safety Laboratory, Tulare Branch.
However, calf diarrhea also can result from systemic bacterial infections, pneumonia and other causes such as fermentation of milk in the rumen (rumenitis).
“When mortality associated with calf diarrhea increases, this usually means multiple infectious agents are present which cause more severe disease,” Blanchard says in the August 2012 issue of the California Dairy Newsletter.
Source: California Dairy Newsletter, August 2012