Premature Foals: Short- and Long-Term Problems
"Gestational age (the maturity of the fetus) varies very widely--some are very mature at 312 days, while some have a ways to go at 380. The question to answer is: Will the foal be a $10,000 money pit with no idea of his chances, or will it have a good athletic career?" posed Robert Franklin, DVM, Dipl. ACVIM, of Goulburn Valley Equine Hospital in Victoria, Australia, during the Western Veterinary Conference held Feb. 15-19 in Las Vegas, Nev. "Don't balk at gathering information. Get very detailed histories and take a good look at the placenta."
He described several "favorable events" that let a practitioner "look at this foal and say he's got a shot," including the following:
- Placentitis. Although this might seem to be a very unfavorable event, Franklin explained that with placentitis, the fetus is living in a harsher environment than normal, so his maturation is accelerated in order to get him out of there.
- Healthy, early foal. The spontaneous delivery from a healthy mare (as opposed to a Cesarean section or induction of delivery because of poor mare health) might not be bad.
- High white blood cell (WBC) count (more than 5,000 mg/dL). Although a high WBC is often considered to be a bad sign because it usually indicates immune response to infection, Franklin noted that it's a good sign in the premature foal because it means his immune system is functioning.
- Responsive WBC count (increasing over time). This is also indicative of a functioning immune system.
- Neutrophil to lymphocyte ratio greater than 1 (indicating the immune system is mature).
- Fibrinogen greater than 400 mg/dL (indicating inflammation in response to a harsh environment).
- Low lactate (indicating an appropriate oxygenation of tissues; this parameter has also been used to predict survival in human intensive care patients).
- Radiographs that show proper cuboidal bone ossification in the knees and hocks. When these bones are still minimally ossified (converted from softer cartilage to bone), they can easily become crushed under the foal's weight. This is more of a concern for future soundness and performance than an immediate, life-threatening issue.
- High creatinine levels, indicating placental dysfunction. The logic of this is similar to that of placentitis being a good thing for these foals--the harsher the uterine environment, the quicker the foal will mature and the younger he can survive. "Creatinine at 18.8 mg/dL might indicate kidney failure, but the neonate is probably too young to have damage that severe!" he said. "If itï¿½s completely related to the placental dysfunction, that level will drop in three to four days."
- A bright overall demeanor at 24 hours. "By this time, the good ones are getting stronger, but the weaker ones will hit a wall even if they improved initially," Franklin explained.
- A normal blood pH (measure of acidity). This should be 7.36-7.40.
- Milk electrolytes indicative of the mareï¿½s readiness for foaling. These include a potassium concentration higher than a sodium concentration and an increase in calcium. "When you see that, you know the foal has been cooking long enough," he said.
Franklin also described several factors that can contribute to a poor outcome for the premature foal, including the following:
- Cesarean section delivery. "You've got to look at the milk first--if the calcium has risen, then he'll probably be OK, but if not, then he isn't ready!" he stated.
- Induction of delivery. "Again, wait for the milk to be ready before you do this," he said.
- Twinning. This is a problem especially for the smaller of unequal twins.
- Systemic illness in the mare.
- Low WBC count.
- A WBC count that doesn't increase by 24 hours of age (an increase of more than 5,000 cells/dL is desired).
- Low neutrophil:lymphocyte ratio. This tells you the immune response is immature.
- Fibrinogen less than 300 g/dL, which indicates a lack of development in a hostile environment.
- High lactate and/or lactate concentration that does not decrease (indicating compromised oxygen delivery to peripheral tissues). "Even if the foal is going to die, it might show some improvement at 12 hours with aggressive intensive care," he said. "Don't rely on early lactate tests to predict outcome, but use them to guide therapy."
- Incomplete ossification of the cuboidal bones (again, this affects future performance rather than immediate survival).
- Low (acidic) pH of the blood (lower than 7.36).
- An overall "sinking" in appearance at 24 hours.
- Normal placenta. Again, a normal placenta will not stimulate the foal to mature more quickly, as a placentitis-affected one would.
- Undeveloped udder in the mare.
- Low levels of calcium in the milk.
Several problems commonly develop in premature foals, some of which can require some tough decisions by the owner and practitioner. Franklin discussed six of these as follows:
- Severe respiratory problems. "If you don't have a ventilator for the foal, do you refer him to a larger hospital?" he asked the audience. "If the owner isn't willing to deal with this or the hospital doesn't take them on, then you have to make a difficult decision."
- Immune system problems. "Make sure they get good colostrum or plasma transfusions, whether from the dam or another source," he said.
- Skeletal problems, such as flexor tendon laxity.
- Dermatological (skin) problems. "They tend to have very thin skin and develop very ugly pressure sores when they're down," he said.
- High nutritional energy needs. "It can take up to ten times the amount needed for normal foals to get them to gain weight," he said.
These are primarily orthopedic in nature, Franklin said, and can include knee and hock problems along with decreased overall performance. Foals with immature cuboidal bones should not be turned out until these bones are more ossified, he noted.
Tarsal crush (crushing of the hock cuboidal bones) is classified as type 1 or 2 depending on the pathology present, he explained. Type 1 describes a ramped tarsal bone (narrower at one end than the other) rather than one that is symmetrical, and these are not associated with poor future performance. Type 2 denotes a bone with a "squeezed toothpaste tube" look, with some bone mass squeezed out in front of the dorsal (front) surface of the cannon bone. This type is associated with poor performance.
"Prompt referral of the premature foal increases survival," Franklin concluded. "Spend the money early on for the tests you need. The cost of the tests might be around $200 and go up as high as $500, but an ICU (intensive care unit) foal can run up a $1,500 bill per day. You need all the information to make the right decisions for these foals."
About the Author
Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.