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Premature Foals Can Have Multiple ProblemsBy Kentucky Equine Research Staff · March 19, 2013

The average length of pregnancy in mares is about 342 days, but this can vary by a couple weeks in either direction and still be considered normal. Some mares have a tendency to have longer or shorter pregnancies year after year, while others are more unpredictable. In general, however, a foal born at or before 320 days of gestation is considered premature.

In general, the closer the birth is to 342 or more days, the better the chance is that the foal will live. Foals born after 300 or fewer days of pregnancy have a lower chance of survival, possibly as low as 10%. However, many premature foals do well with supportive care, eventually growing as well as full-term foals and catching up by or before two years of age.

Some foals born after a pregnancy of normal length may be small and weak with underdeveloped body systems, even though they seem to have had plenty of time to mature. These foals are dysmature rather than premature, and their lack of development is often due to a problem with the placenta or uterus.

Immature respiratory and digestive systems may cause problems in foals that are born prematurely. Even those that seem to be doing well at birth may develop difficulty breathing within 24 hours, requiring supplemental oxygen and other respiratory therapy to clear the lungs. Premature foals that are very small run the risk of aspirating fluids as they nurse because of the abnormally stretched neck position needed to reach the mare’s udder. These foals can be bottle-fed until they grow tall enough to reach the udder easily, or they can be placed on a ramp or platform to get them closer to the mare as they nurse. Either method is fairly labor-intensive because the digestive tract may be able to handle only tiny amounts of milk at frequent intervals.

Premature foals may have skeletal systems that are not yet strong enough to support their weight. Foals that stand for long periods on immature bones and joints are at risk for skeletal damage, so their management may include keeping them from standing too much. These foals will need to be turned from side to side frequently and bedded on foam mattresses or water beds to prevent pressure sores. Even if immediate skeletal damage does not appear to be severe, these foals may have arthritis in later years. Bracing or splinting can help prevent damage to the premature foal’s leg bones until the skeleton becomes stronger.

Infection is another risk for a premature foal because the mare may not have produced enough antibodies in her colostrum, the foal may not have ingested enough colostrum, or the foal’s gut lining may not have been capable of absorbing antibodies from the mare’s colostrum. A blood test can be used to check the foal’s immunogammaglobulin (IgG) level and steps can be taken to support immunity.

Caring for premature foals can be done at home, but it is usually better to send these foals to a veterinary clinic to ensure their needs are met. Around-the-clock attention is often needed to guarantee the foal is maintaining body temperature, staying hydrated, passing urine and feces, and not showing signs that other problems may be developing