The term neonatal encephalopathy is used to describe a variety of behavioral disturbances in a newborn foal. It may also be called neonatal maladjustment syndrome, hypoxic ischemic encephalopathy, or “dummy foal” syndrome. A history of difficult birth, premature placental separation, or placental inflammation may be noted, or the birth could have appeared normal. It is believed to result from decreased oxygen reaching the foal’s tissues during birth. This causes varying degrees of damage to the central nervous system, depending on the age of the fetus, the length of oxygen deprivation, and on how low the oxygen level was. The central nervous system signs may be the most obvious, but other systems, such as the kidneys, heart, gastrointestinal tract, and lungs, may also be affected by the oxygen deprivation.
Signs vary, ranging from a slow suckle response at birth to hyperexcitability, aimless wandering, depression, lying prone, loss of muscle tone, and seizures. In a common scenario, the foal appears normal at birth and progressively loses interest in its dam, loses its suckle reflex, can no longer stand, and begins to have seizures. The foal may start vocalizing, which has been described as sounding like a barking dog; thus, the term “barker foal” is also sometimes used to describe this condition.
If the foal does not also have an infection or limb paralysis, the outlook for neonatal encephalopathy is fair to good: about 80% of these foals recover and grow to be normal adults. With good supportive care, improvement can be seen every day. Mildly affected foals can recover in 2 days, but more severely affected foals may take more than a week before they are able to recognize their dam and suckle.
Providing warmth and nutrition is essential. If the foal does not have a suckle response, it should be tube-fed mare’s milk or an appropriate mare milk substitute to keep it hydrated and maintain glucose levels. Foals should be fed 20 to 30% of their body weight over each 24-hour period. Antibiotics are often given to prevent secondary infections. Treatment may be needed to control seizures, and a protected or padded environment and a human holder to cradle the foal when recumbent can prevent the foal from injury during seizures. These foals are especially susceptible to eye trauma during seizures. A plasma transfusion may be needed if the foal did not receive enough colostrum (initial milk from the dam that contains antibodies).
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