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.