Page 58 - November 2015

If the mare is NI positive, with antibodies against a certain blood type, the foal is at high risk. “We manage the foal to make sure he does not nurse the mare and ingest her antibody-rich colostrum,” says Lu. “We provide colostrum to that foal from mares that don’t have the dan- gerous antibodies. Here at Hagyard, we have a colostrum bank. People donate colostrum from mares that are NI negative. Or you can give
a colostrum substitute, but mare colostrum is best for the foal,” she explains.
The foal must be muzzled, so it can’t
nurse its mother when there’s no one there to supervise. “We also strip out the mare for about 48 hours (with frequent milking) and then do another test to make sure it’s safe for the foal to nurse. Once all the colostrum has been stripped out, the foal can nurse his mother.”
TesTing The Foal
Another test can be done to know if you must go through all this precautionary man- agement or to know when it is safe to let the foal nurse after doing all this. “We can do a JFA (jaundiced foal agglutination) test, mixing a sample of the foal’s blood with a sample of the mare’s colostrum. If there are a lot of anti- bodies against the foal’s red cells, this mix will clot at a certain ratio, creating clumps. If the clotting ratio is 1 to 16 or higher, it is consid- ered positive and the foal should not nurse that colostrum. Many labs will run this test, using a centrifuge,” Lu says.
“This is a serial dilution of the mare’s colostrum in the presence of the foal’s red blood cells,” says Slovis. “This test gives you a dilution level, and the veterinarian can decide whether it’s safe for the foal to nurse the mare. You may get lucky and find no antibodies, and then you can let the foal nurse,” he says.
The foal is safe until he is born. He is at risk as soon as he drinks her colostrum since it contains a representation of all her antibodies.
Horse owners can also do a simple test to get a rough idea about whether the colostrum is safe. Simply collect a drop of blood as the foal’s umbilical cord breaks, and this blood can be mixed with a drop of colostrum from the mare’s udder on any clean surface or a glass slide. If the mixture clumps - due to clumping together of the foal’s red blood cells - this means there’s an incompatibility. If the mixture remains creamy pink, this means it will probably be safe for the foal to ingest the mare’s colostrum.
“If the foal is 12 or more hours old and you think he already has NI and a low red blood cell count, but you are not sure, there are two things you can try,” says Slovis. “If the foal is young enough and the mare still has colostrum, you can do a JFA test on a sick foal. But if the foal is 4 or 5 days old, you can’t do this test because the mare no longer has colostrum. At that point, you could do a Coombs test. It’s not specific for NI, but can tell you whether there are antibodies in the foal’s blood against the red blood cells.”
TreaTmenT
“When we see these foals at the farm, we usually refer them to the hospital for treat- ment because they can become really sick, very quickly. The red blood cell breakdown prod- ucts in their body can lead to bilirubin buildup that can affect the kidneys and brain,” says Lu.
In a severe case, the foal becomes very ane- mic because there are no longer enough healthy red blood cells to carry oxygen around the body. Normally, a foal might have a packed cell volume (hematocrit) of about 30% or higher. Some of these anemic foals have a value of less than 10%. That’s when a blood transfusion may be needed. Often, the best donor is a geld- ing with no history of blood transfusions or any treatment with blood-based products. Some equine hospitals keep geldings to be used as universal blood donors. It’s a simple procedure: the donor horse is restrained in stocks, the col- lection bag is filled with blood, then transfused into the foal.
Another option is to use the mare’s blood to obtain red blood cells, but these must be sepa- rated from the plasma that contains antibodies. “We can use her red blood cells, but we need
to wash them. It takes more time than a blood transfusion,” says Lu.
“Other aspects of treatment are supportive: treating anemia; turning off the foal’s immune system (with steroids) because it’s fighting
the antibodies; and possibly using antibiotics because he is vulnerable to sepsis from other sources. If the foal becomes quite sick, he also needs fluids. It can be a challenging disease to treat,” she says.
“Prognosis for an NI foal that’s ill and being treated depends on the severity of the condi- tion,” says Slovis. “Retrospective studies have shown that about 75% of the sick NI foals that
A JFA (jaundiced foal agglutination) test can be performed to see if there are a lot of antibodies against the foal’s red blood cells in the mare’s colostrum. Signs of a foal that has become sick from NI are anemia, when there are no longer enough healthy red blood cells to carry oxygen through the body, and jaundice, when red blood cells are destroyed and produce bilirubin. This is carried through the body via the bloodstream and the gums, whites of the eyes, and other mucous membranes look yellow. The foal can become very sick, very fast, as the red blood cell breakdown can affect the kidneys and brain.
56 SPEEDHORSE, November 2015
equine health