The list of bacteria and viruses that can potentially cause diarrhea is quite large.  There are six major pathogens that cause diarrhea in neonatal calves: enterotoxigenic Escherichia coli K99, rotavirus, coronavirus, Cryptosporidium parvum, Salmonella spp., and Clostridium perfringens type C.  The color and consistency of the feces and gross lesions can look similar, no matter the causative agent.  Therefore laboratory identification of the infectious agent and histopathology are imperative to obtaining a diagnosis.  It should also be noted that it is common for more than one pathogen to be causing the disease, and that pathogens causing the disease on a farm can change from year to year.  These facts make it imperative that your veterinarian identifies the causative agent(s) to better establish proper prevention and treatment protocols. 

Clinical Signs: Diarrhea causes varying degrees of fluid and electrolyte loss to the calf resulting in; dehydration, electrolyte imbalance, acidosis, depression, loss of appetite, coma, and death. 

Treatment:  The most common cause of death in diarrheic calves is dehydration, electrolyte imbalance, and acidosis.  Replacement of fluid and electrolytes can be either orally or intravenously depending on severity of illness.  Calves that are standing and have a suckle reflex should respond to oral fluid and electrolyte replacement.  Calves that are weak or unable to rise and/or have a weak or absent suckle reflex will require intravenous therapy.  Your veterinarian should be contacted immediately if there is need of intravenous treatment. 

The increased energy and protein requirements of the diarrheic calf necessitate it getting milk as quickly as possible.  Calves that are being treated with oral electrolyte solutions should not be withheld from milk longer than 24 hours.  Oral electrolyte solutions containing bicarbonate and citrate are excellent alkalinizing agents but have been shown to reduce milk digestibility by interfering with abomasal milk clot formation.  Therefore they should not be used on calves that are receiving milk concurrently. Acetate-based solutions can be fed concurrently with milk.  Systemic antibiotics can be used if deemed necessary by your veterinarian. 

Preventing the Disease: Prevention of neonatal diarrhea in calves is two-fold in nature.  First is insuring, maintaining, and increasing the disease resistance of the calf and secondly is decreasing the concentration of pathogens (bacteria and/or viruses) to which the calf is exposed. 

Disease Resistance in the Neonatal Calf: 

1. Provision of adequate energy, protein, and minerals during the last 3 months of pregnancy for optimal immune system development in the fetus.  Cows and heifers should gain about 1 pound per day for fetus and placenta development.  Adequate nutrition is necessary to maximize colostrum quantity and quality.  Antibodies are proteins and adequate protein intake by the dam helps insure antibody production.  Colostral antibodies are an extremely important supplement to the calf’s innate immune mechanisms in providing disease resistance. 

Serum maternal antibody levels in the calf depend on the amount of antibodies absorbed by the intestine and is dependent on quantity of antibody consumed, timeliness of consumption, and absorptive capacity of the intestine.  Quantity is dependent of quantity produced by the dam, udder and teat conformation, and motherability of the dam.  The ability of the intestine to absorb colostral antibodies begins to decrease at birth, ~ 50% absorptive ability at 12 hours of age, and completely closes by 24-27 hours of age.  The ability of the intestine to absorb antibodies appears to be adversely affected by weather extremes and stresses such as associated with a difficult birth.  Therefore events that increase the time interval from calving to colostrum consumption will adversely affect the calf’s ability to resist disease. This lack disease resistance has been shown to increase the chance of disease, death and decreased productivity in the neonatal period and to continue through the feedlot period. 

2. Specific colostral antibody enhancement using vaccines that contain rotaviruses, coronavirus, E. coli K99, and Clostridium perfringens type C antigens, can be helpful in preventing calf scours.  They must be administered to the dam according to the manufacturer’s recommendations to maximize antibody development in the dam and subsequent secretion of antibodies into the colostrum. 

3. Other products used to provide protection to specific pathogens are oral rotavirus and coronavirus vaccines, which is used to provide protection against intestinal infection by these two viral agents.  This oral vaccine must be administered prior to the calf receiving colostrum.  Products containing antibodies to E. coli K99 can provide short-term protection for the calf.  Your veterinarian should be consulted about these products. 

Decreasing Pathogen Exposure to the Calf:

1. Calving in clean and dry areas. 

2. Calve heifers earlier than the cow herd. 

3. Avoid congregating 

a. Avoid hay feeding in calving pastures by setting aside pastures during the summer to stockpile forage for utilization during calving time. 
b. Move pairs to larger pastures promptly 
c. If hay is fed, use hay feeders and move feeders frequently.

4. Use biosecurity and biocontainment measures for all herd additions: 

a. Isolate, quarantine, and perform appropriate tests on all herd additions. (See section on Biosecurity in the Beef Herd) 
b. Introduce pregnant herd additions at least 30 days prior to the start of calving season.  This will allow time for exposure to new pathogens, antibody development and secretion of antibodies into the colostrum. 
c. Do not add calves to the herd until the youngest calf in the herd is over 30 days of age.  Buying a calf at a livestock auction or from a dairy for a cow that has lost a calf can introduce diseases that your herd may not have immunity against.

5. Isolation and treatment: 

a. Remove sick calves from the herd immediately.  One sick calf can produce overwhelming pathogen exposure by shedding as many as 100 million bacteria or viruses per milliliter of feces (500 million bacteria and or viruses per teaspoon of feces). 
b. Treating the sick calves should occur after handling the well calves.  Clean and disinfect all equipment.  Clothing, boots, gloves, etc. worn while treating sick calves should not be worn when handling well calves.

Take Home Message:

1. Bacteria and/or viruses and decreased calf resistance primarily cause calf diarrhea complex to disease. 

2. The affects in the calf include; dehydration, electrolyte imbalance, acidosis, increased energy requirement, loss of appetite, depression, and death. 

3. Treatment is based on replacement of fluid and electrolytes. 

4. Prevention is two-fold and based on increasing the calf’s resistance to disease and decreasing the calf’s exposure to disease (pathogens). 

5. Identify problems early and work with your veterinarian. 

6. Remember mother nature’s disease prevention method.  If the population of a species in an area increases to the critical point of overpopulation, three things can happen that lower population pressures:  1) Increase in predators, 2) starvation, or 3) disease.  The result is a well-fed manageable population that has a high degree of resistance to disease.