Neonatal maladjustment syndrome (NMS) – also referred to as dummy foal syndrome – is a condition that causes neurological symptoms in foals.

This condition prevents the foal from performing normal behaviours, such as recognizing and feeding from the mare, standing and walking. Affected foals may appear lethargic, depressed, or display more serious clinical signs.

NMS can be caused by oxygen and nutrient deprivation in the foal before birth. It may also be caused by a failure of placental hormones to drop following birth.

NMS affects approximately 1-5% of foals and is primarily found in thoroughbreds. [1][2]

Although dummy foal syndrome is alarming to horse owners, the prognosis is generally good so long as the foal does not have any other health complications.

Neonatal Maladjustment Syndrome

Dummy foal syndrome is also known as neonatal encephalopathy or neonatal maladaptation syndrome.

Foals that have NMS are sometimes referred to as dummies, barkers, convulsives, or wanderers – terms that describe some symptoms of NMS. [3]

Foals diagnosed with NMS are usually divided into two categories: (1) normal at birth; and (2) displaying clinical signs at birth.

Normal at Birth

The first type of foals with NMS are born at term and initially appear healthy and normal. The foal will stand and nurse, but after a few hours will develop abnormal behaviours.

Affected foals will typically no longer recognize their mother (due to vision problems or confusion) and will be unable to suckle from the mare. [4]

Type 1 NMS is often associated with trauma to the chest while the foal passes through the birth canal. [5] The progression of NMS will vary depending on the foal and the specific causative factors.

The foal may wander aimlessly, unaware of his surroundings, or may lose his ability to stand completely. The foal might also flail his legs or may be completely limp.

Severely affected foals are unable to stand and will alternate between having seizures and falling into a coma. The foal’s temperature and heart rate rise during seizures and drop when the foal enters the coma. [6]

If the foal recovers, improved mobility is usually the first noticeable sign of recovery. The foal will learn or re-learn to stand, regain awareness of his surroundings, begin to recognize his mother and his suck reflex will return. [6]

Symptomatic at Birth

Type 2 foals are often born prematurely or experience complications during delivery. Type 2 foals may be underweight at birth and are more likely to have experienced inadequate conditions such as oxygen deprivation, before birth. The foal will begin to show signs of NMS before it is 4 days old, although symptoms are usually present immediately at birth. [5]

Healthy foals typically stand within an hour of birth and begin to drink from the mare within 2 hours of birth. [7]

Foals born with NMS usually will not stand and will have no suckle reflex, which prevents them from drinking from the mare or even a bottle. The foal will be very weak and will likely develop sepsis. Type 2 foals are prone to the same symptoms as type 1 foals, and their recoveries follow the same sequence.

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Signs

Foals that develop NMS will usually show a number of the following symptoms, which may come and go or may change as the condition progresses: [1][6][8]

  • Seizures
  • Tremors (shaking) in head and neck
  • Weakness or lethargy
  • Blindness
  • Staggering
  • Legs splayed; difficulty standing
  • Stiff legs
  • Disinterest in the mare or lack of recognition of the mare
  • Loss of suck reflex
  • Walking into things (due to blindness or lack of awareness)
  • Recumbency
  • Flailing legs while recumbent
  • Restlessness or over-excitement
  • Intermittent com