Colostrum: Nothing Better Than Mother's Milk

There might be ongoing debate as to the value of a woman's colostrum versus commercial colostrum products, but for a foal, nothing is better than a mare's milk. Colostrum is specialized milk secreted during the first 24 hours following birth and is characterized by a high content of protein and antibodies. These antibodies are a foal's first line of defense against potential infection. However, if a foal is unable to nurse, or the mare does not produce an adequate concentration of colostrum, the foal's health might be at risk. Giving a foal supplemental colostrum, or a commercial colostrum substitute, might be necessary to save the foal's life.

There is nothing better for the foal during the first 24 hours of its life than its mother's colostrum, claims Michelle LeBlanc, DVM, of the College of Veterinary Medicine at the University of Florida, Gainesville. Commercial products will increase the foal's IgG (immunoglobulin or antibodies) to an adequate level if you give enough. However, if you give the foal the same amount of antibody using the mare's colostrum, the foal will absorb more antibodies and be less susceptible to infection.

Unlike a human fetus, an equine fetus does not receive protective antibodies through maternal transfer during gestation. Thus, a foal leaves the protection of its mother's womb without the necessary antibodies to ward off neonatal diseases. A foal receives its life-sustaining antibodies by ingesting its mother's colostrum.

When a foal does not ingest a sufficient concentration of antibodies to protect it from bacterial infection, it is said to suffer from failure of passive transfer. Failure of passive transfer can stem from a foal's inability, or unwillingness, to nurse. The mare might also contribute to failure of passive transfer if she rejects the foal, is injured or ill, or prematurely drips milk. Premature dripping of milk, or streaming, dilutes colostrum, thus the foal does not get the optimum concentration of protein and antibodies for fighting infection.

The amount of antibody in the colostrum can be estimated with an equine colostrometer. The colostrometer measures specific gravity that is highly correlated to the amount of antibody in the colostrum. A specific gravity of 1.06 or greater indicates that the colostrum has an adequate antibody level.

The colostrometer was developed by LeBlanc, an equine researcher, with the help of engineers at the University of Florida. Equine practitioners and researchers consider an IgG transfer of 800 milligrams per 100 milligrams of blood into a foal's bloodstream a successful transfer of antibodies. IgG levels between 400 to 800 are noted as partial failure of passive transfer, but might be considered adequate depending on environmental conditions. IgG levels less than 400 indicate failure of passive transfer.

Mare managers and/or veterinarians measure IgG levels by drawing blood from the foal and separating the serum from the blood. The IgG level in the serum then is measured using commercially available rapid test kits. If it is determined that a foal's IgG level is too low, then supplemental colostrum or gamma globulin can be administered orally if the foal is less than 24 hours old. Older foals must be given plasma or gamma globulin intravenously because after 24 hours, a foal's gut "closes" and is unable to absorb the antibodies.

There are special epithelial cells in the small intestine that allow for the absorption of large molecules (maternal antibodies and other colostral proteins), LeBlanc said. Once the foal has suckled a certain amount, or 24 hours goes by, whichever comes first, the special cells slough off. Once the cells slough off, the intestines can no longer absorb the large molecules and transfer them to the bloodstream.

Mother Nature shuts down the gut as a line of defense against harmful bacteria. If the gut did not shut down, the foal could absorb harmful bacteria through the special cells, i.e., E. coli or Streptococcus zooepidemicus.

LeBlanc prefers supplementing deficient foals with colostrum before 18 hours of age because administration of plasma or concentrated gamma globulin products intravenously is expensive and time consuming.

Most veterinarians do not consider IgG levels between 400 to 800 to be a problem. However, foals within the 400 to 800 range might succumb to infection if they are subjected to unfavorable environmental conditions, i.e., dirty stalls or paddocks, rain, cold, or over-crowding. A foal which experiences failure of passive transfer has more potential to get sick since the foal has not acquired the necessary antibodies to fight off infection.

A veterinarian must evaluate the foal's environment to determine whether or not the foal needs supplemental colostrum, LeBlanc said. If farm management is good, the stall is clean and dry and there are no drafts, the foal is much less likely to get sick.

If the foal is too weak to nurse, is injured, or is rejected by the mare, the mare can be milked of her colostrum and the foal fed with a bottle. If the foal will not accept a bottle, the veterinarian might choose to administer the colostrum through a nasogastric tube--through a nostril, down the esophagus, and into the stomach. If the problem is with the mare, i.e., the mare streamed milk or has poor-quality colostrum, then the veterinarian might use frozen colostrum from another mare if it is available. If natural colostrum is not available, a veterinarian can administer commercially produced plasma, gamma globulin, or oral IgG.

The problem with commercial products is that they are not as effective as a mare's colostrum in fending off specific infection and disease. There are many substances in colostrum (besides antibodies and proteins) that are just as important in protecting a foal from infection, LeBlanc said. Although commercial products have high levels of antibodies, they do not necessarily have the other substances that help a foal fight infection.

"Until we are able to identify what those substances are, we will really never be able to come up with a commercial product that is as good as a mare's colostrum," said LeBlanc.

Since a mare's colostrum offers the foal its best defense against infection and disease, LeBlanc recommends breeders institute prenatal care programs to ensure that mares have every chance to produce quality colostrum.

"The major cause of streaming (colostrum) in mares are placental abnormalities," LeBlanc said. "The best way to avoid placental problems is to have good farm management, which includes regular checkups, good nutrition, clean surroundings, well-ventilated barns, and not stressing the mare in the final trimester of pregnancy.

"When a mare streams or drips milk prematurely, she is also streaming antibodies that should be ingested by the foal. By the time the foal is born and nurses, the concentration of antibodies may not be enough to ensure protection against infection.

"If a mare streams milk, our first concern is that something abnormal is going on with the placenta," LeBlanc added. "If after examination we determine she has contracted an infection, we consider her pregnancy to be high risk and will monitor her progress and treat her with antibiotics and progesterone."

In some cases, a mare might not produce any milk. Although veterinarians and researchers have not pinpointed all the reasons a mare does not produce milk, they do know that fescue toxicity can inhibit milk production. Fescue grass is common in pastures throughout the Southeast United States. However, the fescue grass can be infected with an endophyte that is beneficial for grass growth, but harmful to horses. When a mare ingests endophyte-infected fescue, it can affect the mare's endocrinology. She might not bag up to produce milk and/or might have prolonged gestation.

Infestation can be detected by a lab test, but about all that can be done to combat endophyte-infected grass is to remove the mares from the infected grazing areas.

"If a mare has been grazing on infected grass, removing her from the grass before she is 300 days into her pregnancy will usually forestall complications due to fescue toxicity," said LeBlanc. "If a mare has been streaming milk, a determination must be made as to whether or not she has enough antibodies left in the colostrum to protect the foal from infection. Again, if the foal's IgG level is low, then the foal should be given supplemental colostrum, preferably from the mare. A commercial source of antibodies can be given if necessary."

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Aleta Walther

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