Congenital cleft palate in horses is an uncommon deformity affecting approximately 0.1-0.2% of the equine population. The condition is a malformation of the soft and sometimes hard palate where the left and right side fail to unite, forming a cleft. It is usually recognized shortly after birth when the foal starts nursing. The most common clinical signs include milk coming out of both nostrils and coughing while nursing. Some foals with smaller defects in the palate are not thrifty and develop recurrent lung infection. Larger palatal defects produce more severe clinical signs and are life-threatening because of aspiration of milk and feed material into the lungs. Therefore, early detection and correction of the condition are important to reduce the severity of aspiration pneumonia.
If you suspect that your foal may have a cleft palate, call your veterinarian immediately. In addition to thorough physical and oral examinations, your veterinarian will need to perform additional diagnostic tests such as endoscopy and x-rays. Endoscopy of the throat area is essential to defining the extent of the cleft. X-rays of the lungs will help to determine the severity of pneumonia caused by aspiration of feed material. Both the extent of the cleft and the presence of pneumonia are key determinants for prognosis when considering treatment for cleft palate.
The only current treatment for congenital cleft palate is surgical correction of the cleft. This procedure involves either splitting the lower jaw or creating an incision in the throatlatch region to provide access to the defect. The surgery can be technically quite demanding due to the depth of the incision and poor visibility. Complications are common (greater than 85%) following surgical correction and include: complete or partial breakdown of the repaired palate, incisional infections, and continued aspiration of feed material. Even successful repairs will often require more than one surgery to achieve complete healing of the palatal defect.
After surgery, special care of the foal is essential and includes long-term antibiotic treatment and special feeding procedures for 2 to 4 weeks. The soft and hard palates are exposed to high numbers of bacteria from the environment; antibiotics help to prevent infection in the repaired palate, as well as treat any underlying lung disease. Special feeding procedures are necessary to reduce strain on the palate after surgery. Foals are allowed to nurse milk following surgery but are restricted from solid food (hay and grain) for several weeks. Alternatively in older foals, a pelleted gruel may be fed through a stomach tube or an esophagostomy (hole into the esophagus). The latter procedure has fallen out of favor due to complications associated with the esophagostomy site.
Despite the high complication rate, surgery can be successful in some cases. Certainly foals with smaller defects that affect only the soft palate have a better chance for survival following surgery than those with large defects involving both the hard and soft palates. As many as 50% of surgically-treated horses have had complete healing of the palatal defect following one or more surgeries.
However, even with complete healing of a repaired cleft palate, athletic potential may be compromised. This is due to dysfunction of the muscle tone of the soft palate. Palatal muscles normally serve to tense the palate so it does not collapse into the nasopharynx. When these muscles are abnormal, the soft palate can "billow" and obstruct the airway during exercise, causing an upper airway noise and early fatigue.
Another concern when considering treatment for cleft palate is the potential heritability of the condition. Though heritability has not been proven in horses, a strong correlation has been found in humans. Because of the concern for passing undesirable, life-threatening traits on to offspring, we advise not breeding any horse that has received a cleft palate repair. Additionally, it may be ill-advised to repeat the breeding cross that resulted in an affected foal.
In conclusion, congenital cleft palate of the horse is a difficult condition to treat and has some heritability concerns. Though uncommon (affecting 1 to 2 foals in every thousand), cleft palate is an important disease because of its life-threatening potential. Contact your veterinarian immediately if you notice that your foal has milk coming out of either nostril or seems to cough frequently while nursing. If your foal is diagnosed with a cleft palate, the decision for surgical repair should not be taken lightly. Surgical repair should be elected only after careful consideration of the potential drawbacks.