Foal Diarrhea

Q:I am a new owner of a broodmare who just had her first foal, which now has diarrhea. What can I do about it? How serious is it for him? How do I keep this from happening again?

A:The causative agents for diarrhea can be bacteria, viruses, parasites, or a range of non-infectious agents or conditions such as toxins, lactose intolerance, or "foal heat" diarrhea. Foal heat is due to normal physiological changes in the foal's gut and usually occurs anywhere from day seven to 12 after birth. Infectious agents that can cause diarrhea include rotavirus, Salmonella, Rhodococcus equi, clostridial organisms, and Actinobacillus. However, when it comes to diagnosing diarrhea, veterinarians often are hard-pressed to pinpoint a specific cause. Also, once infectious diarrhea has been diagnosed in a foal, that foal should be isolated from other foals to prevent spread of the infection.

One of the main factors in whether a foal becomes afflicted with diarrhea is whether or not the foal received enough colostrum, or whether the colostrum was of good quality. Colostrum contains antibodies that fight off the viruses and bacteria the new foal faces in the first few weeks of life. A blood test done by your veterinarian at 12 hours of age will indicate if the foal nursed enough quality colostrum.

The first 18 hours of the foal's life are critical when it comes to the absorption of colostrum. It is during that window of opportunity that the foal's gastrointestinal system can absorb the antibodies found in the colostrum. The mare produces antibodies against bacteria and viruses by vaccination or exposure to these organisms in her environment. The colostrum protection is essentially the only protection a foal has against harmful germs. Foals are born with an immature immune system that has to develop for about 30 days in order for it to produce antibodies on its own.

Look at the mare's udder twice daily. A full udder means that the foal is not adequately nursing, getting nutrition, or replenishing its fluids.

It is important for a veterinarian to evaluate diarrheic foals less than 30 days old because they can develop life-threatening dehydration in as few as six to eight hours. Dehydration occurs quickly in young foals because of their small size and because their gastrointestinal systems are short and do not reabsorb as much liquid from their feces as adult horses. Foals older than 30 days can also develop severe diarrhea which needs immediate veterinary attention.

Treatment for foals under 30 days of age with serious diarrhea often consists of intravenous fluids. This not only replenishes the lost fluids but can help correct electrolyte imbalances such as low  potassium, sodium, and chloride. Glucose is also provided in many IV fluid solutions. If serious electrolyte imbalances are not corrected, other organs can be adversely affected, such as the heart. Also, a protectant, such as equine version of Pepto Bismol, can be used to coat and soothe the gastrointestinal tract.

Owners should not reach for antibiotics when they discover a foal with diarrhea. Indiscriminate use of antibiotics can complicate some diarrhea cases by killing off "good" bacteria found in the foal's gut. Antibiotic decisions should be left to the veterinarian.

Good farm management is key to preventing diarrhea. These practices include the following:

  • The higher the concentration of animals on land, the higher their risk of exposure to organisms that cause diarrhea. Do not exceed more than two horses per acre.
  • Make sure the foal gets good-quality maternal colostrum in sufficient amounts in the first 18 hours of life.
  • Do not move new mares and foals in with the resident population immediately. Either group might be carrying an infectious disease.
  • If you are in an area where rotavirus is known to be a problem, you should vaccinate the mare before she gives birth in order to pass on the antibodies to the foal through the mare's colostrum. The vaccination, which can be obtained from your veterinarian, should be administered to the mare at eight, nine, and 10 months of gestation.
  • Chain harrow pastures where horses are kept to break up manure piles and expose parasites and other organisms to environmental conditions.
  • Make sure the foal is born into a clean environment. Disinfect the stall in which the foal is born to protect the foal from bacteria  and viruses using a phenolic disinfectant.
  • If you are moving a pregnant mare to a different barn, make sure to transport her four to six weeks before she foals. This time will allow her body to build up antibodies to the local pathogens in her new environment, which will then be passed on to the foal in the colostrum.

About the Author

Roberta Dwyer, DVM, MS, Dipl. ACVPM

Roberta Dwyer, DVM, MS, Dipl. ACVPM, is a professor within the University of Kentucky's Maxwell H. Gluck Equine Research Center and editor of Equine Disease Quarterly.

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