by: Michelle Arnold, DVM
University of Kentucky Extension

Diarrhea in neonatal calves is one of the leading causes of morbidity (sickness) and mortality (death) in North America and Europe and continues to be a major cause of economic loss to the beef cattle industry. There are five major infectious causes of diarrhea in calves less than 21 days of age: E. coli K99, Rotavirus, Coronavirus, Cryptosporidia, and Salmonella. Other factors such as inadequate colostrum, poor sanitation, stress, and cold weather can make calf survival almost impossible. Regardless of the cause, diarrhea results in loss of electrolytes and water in the feces of calves and decreases milk intake. Ultimately, this leads to dehydration, metabolic acidosis (the blood is more acidic than normal), electrolyte abnormalities, and a negative energy balance from the lost nutrients and lack of milk. Oral electrolyte solutions have typically been used to replace fluid losses, correct acid-base and electrolyte levels in the blood, and provide nutritional support with the added benefit of being relatively inexpensive and easy to administer. Recent research has resulted in better methods to assess and treat a calf with diarrhea as well as better guidelines for choosing an oral electrolyte solution.

The most common mistake made in the use of oral electrolyte replacement therapy is waiting too long before administering these formulas or not giving them often enough to affected calves. Administered early and frequently, these fluids help the calf maintain strength and normal body temperature and allow it to continue nursing. Administering fluids too late, when the calf is already depressed and down, or administering too little so that the calf continues to lose more fluid than it is receiving orally, allows

the dehydration to worsen and the calf's condition to deteriorate. When dehydration and acidosis get severe enough, the gastrointestinal tract loses function and orally administered fluids are no longer of any value. In these cases, the only effective means of preventing death is to have a veterinarian administer intravenous fluid therapy.

A quick assessment of a calf with diarrhea will determine if oral fluid therapy or if intravenous (IV) is needed. The choice depends on the severity of both dehydration and metabolic

acidosis (low pH of the blood). Dehydration is relatively easy to monitor by how far the eyeball is set back into the skull and the loss of skin elasticity. Metabolic acidosis is assessed by the calf's ability to stand and suck. In general, a standing calf with a strong to moderate suckle reflex or that demonstrates a "chewing action" can be given oral fluids. Mildly dehydrated calves showing mild skin tenting when the skin on the neck is pinched, minimal sinking of the eye into the head, eyes and mucous membranes are still moist, and extremities are still somewhat warm are ideal candidates for oral fluids.

Thumb rules for the use of oral electrolyte fluid supplements for scouring calves:

1. Reconstitute the oral electrolyte supplement and administer it according to manufacturer's recommendations.

2. Administer the reconstituted fluid formulation at approximately five percent of body weight, which is 2 quarts for an 80 pound calf. How many times per day this is necessary depends on how much fluid the calf is receiving by nursing and how much fluid is lost through the diarrhea. In many cases, the progression of the disease is not very rapid and the problem lies only in the missed opportunity to administer oral fluids at an earlier stage when response is best. Continued assessment of the scouring calf's condition is required in order to make good decisions regarding the frequency of fluid administration.

3. Only administer oral fluids if the calf still has a suckle response. It is usually better to administer oral fluids by bottle with voluntary suckling. This enhances passage of the fluid to the abomasum via the esophageal groove. Oral fluids can be given by esophageal feeder when the suckle reflex is weak, but this method places fluids into the rumen. Any calf with a very weak or absent suckle reflex should be given IV fluid therapy because, if oral fluids are given to a calf with ileus (no gut motility), the fluid is not absorbed but instead pools in the rumen resulting in bloat and/or rumen acidosis. ANY calf that is severely depressed and unable to stand requires intravenous fluids.

4. It is extremely important that the oral fluids chosen for rehydration will be able to increase blood pH from an acidic state to a more neutral state. This is normally accomplished by alkalinizing agents such as bicarbonate, acetate, or propionate found in oral electrolytes. Although all have similar effects, acetate and propionate are preferred over bicarbonate in nursing calves because they do not interfere with milk digestion.

5. If calves are depressed and refuse to nurse, a hypertonic oral electrolyte product such as Calf-Lyte II HE or Enterolyte HE can be used. A "hypertonic" oral electrolyte product has a very large amount of glucose (sugar) in the preparation and has "HE" on the label (for "high energy"). Hypertonic solutions can give greater nutritional support because of the higher glucose level yet they can cause abomasal bloat and increased diarrhea if• the calf is unable to absorb this large amount of sugar. If nursing is not resumed within 12 hours, calves will get too weak to respond to oral treatment alone.

6. Milk or milk replacers should NOT be withheld from scouring calves. None of the oral electrolyte formulas provide adequate protein and energy to replace milk. Some experts used to recommend a "rest the gut" approach, suggesting that continued milk feeding worsens diarrhea. However, research has shown that milk feeding does not prolong or worsen diarrhea, nor does it delay healing of the intestines. Calves should be maintained on their full milk diet (continue nursing) plus oral electrolytes when possible as long as they exhibit diarrhea.

Electrolyte fluid administration is by far the most effective treatment for calves with scours. Because affected calves are often weak and chilled, additional nursing care may be necessary for survival. In this regard, providing warmth, dry bedding, protection from the elements, and adequate nutritional support are all critical. Fluid therapy is most effective when it is administered aggressively and early in the course of the disease. The most critical factor may be the early recognition of affected calves. Caught early, most calves will respond very favorably to oral fluid therapy. Remember milk is better at maintaining a normal blood glucose level than any electrolyte solution so allow the calf to continue nursing. If the calf becomes so severely dehydrated it is weak and unable to rise, or if it has no suckle, intravenous fluid therapy may be the only way to save the calf's life. Other treatments, such as antibiotics, may be beneficial but they are far less important than fluid and electrolyte replacement when it comes to calf survival.

Improved diagnostics are now available to ascertain the cause of neonatal calf diarrhea. The UKVDL has a Calf Diarrhea Multiplex PCR panel which tests for the major diarrhea pathogens in calves less than 21 days old including: E.coli K99, Rotavirus, Coronavirus, Salmonella spp., and Cryptosporidia. Submit one fecal sample per calf early in the course of disease and before any treatment has been given. The test is highly accurate as it detects the DNA or "molecular fingerprint" of the various pathogens and results are available within one to two days. At least five grams of feces must be submitted in a labeled, leak-proof container maintained at a cool temperature during transport. Do not submit fecal samples in gloves; screw cap tubes or vials are preferred in the laboratory. Check the website for more information.

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