Diarrhea is the Warning Light

Diarrhea problems are a constant threat to young calves and can cause more financial loss to your operation than any other disease related problem. A well managed program of proper nutrition and sanitation is necessary to minimize incidence of sickness and loss. Learn to recognize common causes of scours in calves.

A photo of diarrhea caused by escherichia coli

Escherichia Coli (E. Coli)

Escherichia coli is almost the only diarrhea that occurs within the first three days of life, often on the first day. The E. coli bacteria releases a toxin that damages the cell lining of the gut, causing the normal absorptive capacity of the intestine to change and results in fluids and electrolytes being secreted and lost. This process can pump so much fluid into the gut that the calf dies before the external signs of diarrhea appear. Prevention involves cleanliness and vaccination of cows followed by proper colostrum management.

A photo of diarrhea caused by the rotavirus and coronavirus

Coronavirus and Rotavirus

The most common viruses associated with calf diarrhea are Rotavirus and Coronavirus. The calf loses the ability to digest and absorb milk. Both of these viruses possess the ability to disrupt the cells which line the small intestine resulting in diarrhea and dehydration. Coronavirus also damages the cells in the intestinal crypts and slows down the healing process in the intestinal lining. Furthermore, the damage caused by either Coronavirus or Rotavirus is often compounded by bacterial infections and the risk for fatal diarrhea is increased when mixed infections occur. Infected calves are severely depressed with excessive drooling and watery diarrhea; fecal color varies from yellow to green.

A photo of diarrhea caused by salmonella


The Salmonella species of bacteria have been associated with calf enteritis but like E.coli, Salmonella has a strong tendency to spread beyond the gut and cause widespread disease. The result of this invasion is damage to the tissue, so that water and food cannot be absorbed. Salmonella can readily invade the rest of the body, causing blood poisoning and rapid death. Salmonella produces a potent toxin or an endotoxin (poison) within its own cells. Clinical signs associated with Salmonella include bloody diarrhea , fibrin in the feces, depression and elevated temperature. The disease is more severe in young or debilitated calves. Infected calves can shed the organism in feces, urine, saliva and nasal secretions, contaminating everything they touch and everything that touches them.

An photo of diarrhea caused by ingestion of a protozoa parasite such as Cryptospordum


Cryptosporidia is another protozoan parasite that is much smaller than coccidia. After ingestion it adheres to the lining of the intestine wall and causes damage to the microvilli, the finger-like projections that are important for absorption of water and nutrients. Cryptosporidia typically does not kill calves except by causing severe dehydration, electrolyte imbalance and acidosis. There is no labeled medication for Cryptosporidia so prevention is important. Treatment of affected calves consists of supportive fluid and electrolyte therapy and antimicrobial therapy to prevent secondary bacterial infection. Calves infected with Cryptosporidia can be saved with good nursing care. Cryptosporidia is also infectious to people so handle infected calves with care.

A photo of nutrition induced diarrhea

Nutritional Diarrhea

Nutritional diarrhea is caused by anything that disrupts a calf’s normal habit of nursing. Calves often suffer from diarrhea which is not caused by an infection but is due to incorrect feeding. Calves should be fed with great care since they react with great sensitivity to any errors and to any irregularity. It is important to look for errors in the nature and composition of feed, errors in preparing this feed and sanitation. If Milk Replacer is being used, ensure components are appropriate to age, product is correctly mixed and temperature is correct at time of consumption! Since the calf is weakened by the diarrhea, bacterial infections can easily supervene. One of the most unrecognized problems in Calf Rearing is the contamination between feed and water buckets. The toxins from moldy feeds cause severe digestive disorders and limit growth.