Page 94 - March 2020

EQUINE HEALTH
DIARRHEA IN YOUNG FOALS
Is it Foal Heat Scours or Something Worse?
by Heather Smith Thomas
One of the most common and least dangerous types of diarrhea in young foals occurs at the time of
the dam’s first heat cycle, which is often called foal heat. This heat period usually occurs any time from four to 14 days after foaling, and usually lasts from one to three days. It has also been called “nine-day heat,” since nine days is about the average time that mares will cycle again
after foaling.
Foal heat diarrhea that coincides with the
mare’s first heat period after foaling seems to be a very normal and universal event. The foal is not sick, unless the problem becomes compli- cated by secondary infection.
Horsemen have believed for many years that hormonal changes during the mare’s heat cycle affects digestibility of the milk in some way, causing the diarrhea. But about 20 years ago, researchers began to think that it must be more complex than that, since orphan foals being fed an artificial milk replacer also tend to develop diarrhea at about six to 12 days of age. This stimulated several studies on the subject.
Research at the University of Florida suggested that foal heat diarrhea is a normal reaction in the gut of the young foal as it gears up to handle solid food. The theory is that the small intestine begins secreting more fluids, enzymes and electrolytes that help with diges- tion, and diarrhea results if the large intestine is not yet developed enough to absorb those extra fluids.
The role of the large intestine is to extract the nutrients from food that has been broken down earlier in the digestive tract, and to absorb the extra water to keep the body from dehydrating. Much of the water absorption of the body takes place in the large intestine. If the large intestine can’t absorb the extra fluid coming through, the result is diarrhea.
We don’t know exactly why diarrhea tends to occur during the mare’s first heat cycle. The fact that foals without mothers also tend to scour sometime during the first two weeks of life suggests some other cause than the mare’s hormones, yet there does seem to be a correlation. For instance, if the mare comes into heat four days after foaling, that’s when her foal scours. If she comes into heat seven days, or nine, or 13 days after foaling, that’s when he scours.
Whatever the cause, or combination of causes, most horsemen breathe a sigh of relief when finding that the mare is in heat when they discover a young foal scouring, because this type of diarrhea usually isn’t serious. But the foal should still be watched closely to be sure he stays perky, strong and vigorous. Simple foal heat scours will not sap his energy nor make him feel ill. He still nurses regularly and will run and play, feel- ing fine. If at any time he seems dull, how- ever, it may be more than foal heat scours.
Intestinal infections can be deadly for young foals, especially in the first days and weeks of life. A clean environment, good care and monitoring, and being proactive to head off or deal with any problems are very important.
Ernest H. Martinez II, DVM, Hagyard Equine Medical Institute, says foals in the first week of life are most at risk so it is cru- cial to quickly and aggressively deal
with any diarrhea at this age that might
be caused by infection. “Those foals can
get really sick, very fast. They dehydrate quickly and their electrolytes get out of balance. Damage to the GI tract from an infection can cause a bacteremia (bacteria in the bloodstream) or septicemia, which can quickly be fatal,” he explains. These young foals have a naïve immune system and the infection may end up in the joints, with more complications later.
If a mare has a full udder and is worried about the foal – nudging it and wanting it to suckle – something is wrong.
SIGNS OF SICKNESS
The foal will be dull, lying around more than usual, and off feed. Often the first clue will be
a mare with a full udder or streaming milk. “At this young age, these foals can go downhill very quickly,” says Martinez. Thus, it is important to identify a problem quickly.
Dr. Eric Schroeder, Department of Veterinary Clinical Sciences, Ohio State University, says at first the foal may seem just a little lethargic and uncomfortable, maybe rolling onto its back and acting a little colicky. If the mare has a full udder, is worried about the foal – nudging it and wanting it to suckle – something is wrong. “A good farm man- ager picks up on these subtleties very fast,” he says.
With diarrhea, a young foal can dehydrate rapidly. “The young foal consumes about 20%
of its body weight daily in milk, nurses often,
and urinates frequently. If the foal is not nursing as much as usual, and continually losing fluid through diarrhea and urine, the end result is dehy- dration. “If there is any wetness on the foal’s tail, even if you are not seeing diarrhea, this is a sign of trouble,” Schroeder says.
You don’t always see the foal passing loose feces or see the watery feces on the ground; it may soak into the grass or bedding. Often the foal’s wet tail or buttocks may be the only clue.
Foals in the first week of life are most at risk,
so it is crucial to quickly and aggressively deal with any diarrhea at this age that might be caused by infection.
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