June 2000

Foal Deaths

by Heather Smith Thomas

Most foals that are lost on breeding farms die within the first few weeks of life, yet many of these losses can be prevented. One study on foal diarrhea (1986-1988), sponsored by insurance company Lloyd's of London and their Kentucky agents, included a collective study of foal deaths undertaken by pathologists at the Livestock Disease Diagnostic Center at the University of Kentucky in Lexington. Most of the 531 foals studied were Thoroughbreds, but there were other breeds represented as well, and the total represented 43 percent of all equine post-mortems done during that year. More than half of the foals, 291 (55 percent), died during the first week of life while the remaining deaths occurred between 8 and 180 days of age.

Of the foals that died during the first week of life, one third did so almost immediately after birth, due to insufficient oxygen leading to heart and respiratory failure. This problem, which is called neonatal asphyxia, is generally due to slow and difficult birth where the foal is either too large or is positioned wrong. Sometimes a mare, particularly one foaling for the first time, may be so nervous and upset when being confined during labor that she refuses to lie down, thus delaying the birth for too long. Other reasons for a foal failing to breathe properly following birth are when foals are born premature and weak, due to an infection of the uterus and/or the placenta. The foal is thus not fully developed and is unable to cope with the environment outside the uterus.

It was found that most of the other losses of foals in the first week of life were caused by pneumonia, digestive tract infections and septicemia (a generalized blood-borne infection within the body). The majority of these illnesses were caused by bacteria, especially E. coli, Streptococcus, Actinobacillus, and less frequently Salmonella. Some infections were developed in the fetus during gestation, resulting in a weak and sick foal at birth, often born prematurely. Some infections were the result of a failure of passive transfer of immunities, due to foals not getting enough colostrum (and its important protective antibodies) soon after birth. These foals were very susceptible to bacterial infections.

Other foal deaths during the first week of life were the result of extreme deformities, such as contracted tendons or legs that would not straighten-abnormalities which are often related to skeletal problems such as a crooked spine and abnormal deviations of the spinal column. Bone fractures, especially rib fractures, which can easily occur as a large foal is forced through the mare's pelvis during a hard birth, are not uncommon in the newborn foal and these can hinder the foal's ability to breathe properly. Many rib fractures, though, will heal if the broken pieces are not displaced. In this case the broken rib may not even be noticed, since the foal shows no symptoms when the fracture is not dislocated prior to healing. Anything that moves the fractured ends out of place however, such as handling the foal and trying to help it stand up, may make a rib fracture life-threatening if the ends of broken bone happen to penetrate the lungs or other vital organs.

Other less frequent causes of death in foals during the first week of life include: ruptured bladder; neonatal hemolytic anemia (also called hemolytic icterus or neonatal isoerythrolysis), in which the antibodies in the mare's colostrum attack the foal's red blood cells after it absorbs the colostrum; hydrocephalus (water on the brain) and other malformations of the head.

Many of the deaths occurring in foals from 8 to 180 days of age were in foals that suffered serious problems soon after birth and later died or were euthanized for humane reasons. Some were also foals with septicemia (generalized infections, including navel ill) that later developed bone or joint infections.

The majority of foals that had no history of illness immediately after birth but died within the next 6 months, succumbed to pneumonia, lung damage, pulmonary abscesses, or to diseases of the gut. Pneumonia cases were commonly caused by an initial viral infection such as rhinopneumonitis, with a secondary bacterial infection, due to Streptococci bacteria, being the actual cause of death. Another bacteria that commonly caused lung damage and abscess formation was Rhodococcus equi, a pathogen that is often present in the soil on horse farms, and which causes a high mortality rate in foals.

Death due to problems in the gastrointestinal tract (stomach and intestines) were due to perforated ulcers; enteritis (intestinal infection) caused by a wide variety of bacteria including Salmonella; torsion and strangulation of the small intestine; as well as several conditions that damaged the liver. The incidence of death from perforated gastric ulcers has declined from rates noted in earlier studies, possibly because more foals had been given anti-ulcer medications as a preventative measure. 

It is obvious that the young foal (right) has problems as he feels more comfortable in this position than lying more naturally on his brisket.

Another problem that showed a decrease in incidence was botulism, as there were only 6 cases of "shaker foal" deaths documented. This decrease was probably due to the wide use of botulism vaccine throughout the U.S. for more than a decade. There were also less deaths from both navel ill (umbilical stump infection) and Salmonella infection than in previous years, as well as very few deaths from neonatal hemolytic anemia. All decreases are probably a reflection of improved management practices on breeding farms and a greater understanding among horsemen of these diseases, how they occur, and of how to prevent them.
Since most foal deaths occur during or soon after birth, many of these losses can be prevented by greater supervision of mares that are foaling and closer examination and care of the newborn foal. The breeding farms that lose the least foals are generally those that implement the most intensive management and supervision systems during foaling.



SIDEBAR

Foal Heat Diarrhea

One of the most common but least dangerous types of diarrhea in young foals occurs at the time of the dam's first heat cycle or foal heat. This heat period usually takes place four to 14 days after foaling and lasts one to three days. It is also called "nine day heat" because that is about the average number of days that mares take to begin to cycle again after foaling.

The 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 really sick, unless the problem becomes complicated by secondary infection. 

Horsemen have believed for many years that hormonal changes during the mare's heat cycle affect the digestibility of the milk in some way, thereby causing the diarrhea. But a few years ago researchers began to think that it must be more complex than that, since orphan foals being fed an artificial milk replacer (no mare's milk) also tend to develop diarrhea at about six to 12 days of age. This theory initiated 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 food. The theory is that the small intestine begins secreting more fluids, enzymes and electrolytes that help with digestion, and if the large intestine is not yet developed enough to absorb those extra fluids, diarrhea results.

The role of the large intestine in the horse's digestion is to extract the nutrients from the food that has been broken down earlier in the digestive tract, and to absorb the extra water, so as 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 the 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 the relationship seems to be more than coincidence. For instance, if the mare comes into heat four days after foaling, that's when her foal scours. If she comes into heat either seven, nine or 13 days after foaling, that's when it scours. So there must, in fact, be some kind of correlation.

At any rate, whatever the exact cause or combination of causes, most horsemen breathe a sigh of relief when upon finding out that the mare is in heat they discover her young foal is scouring, for this type of diarrhea usually isn't serious. But the foal should still be watched closely so as to be sure that he stays perky, strong and vigorous. Simple foal heat scours will not sap his energy nor make him feel ill. He should continue to nurse regularly and will run and play, feeling just fine.

If at any time the foal becomes dull and lethargic, stops nursing or has a fever, or in any other way acts sick or uncomfortable when he has diarrhea, he needs medical attention immediately. Then if infection complicates a case of foal scours, his gut lining will become damaged and he may dehydrate. Serious scours can swiftly kill a young foal.

Generally, foal heat diarrhea will need no medication other than possibly putting mineral oil on the foal's rear end, to keep the acid feces from burning his skin and taking all the hair off. Mineral oil or petroleum jelly applied a couple times a day can help protect his tender skin from the irritation of being covered with diarrhea. Wash his buttocks gently before applying the soothing coating. Keeping his bottom clean and "greased" will make him feel more comfortable and prevent hair loss.

If the foal has watery feces for several days, a little Pepto Bismol (about 30 to 40 cc, the standard adult human dose of about two tablespoons) can be given to him orally by syringe. Stick the syringe, without the needle of course, into the back of his mouth and gently squirt the Pepto Bismol in, a little at a time, as he swallows it. This will sooth his gut and help slow up the diarrhea, making him more comfortable. This type of diarrhea won't need any antibiotic treatment unless complications develop.
-Heather Smith Thomas

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