The Importance of Colostrum for Foals

By Dr. Tom Lenz

Unlike other mammals, mares do not transfer antibodies to their foals via the placenta during gestation, but rather transmit them through colostrum, a yellowy honey-like substance in milk produced in limited quantity around the time of foaling. A foal that ingests its dam’s colostrum within the first 24 hours of life acquires the mare’s antibodies as protection against disease for the first four to eight weeks of life. But according to reproduction specialist Dr. Michelle LeBlanc, more factors come into play that could endanger your foal’s life.

Even if a foal stands and nurses within the first one or two hours of life, it still might be unable to ward off disease if the mare’s colostrum leaked out before foaling, if the colostrum is `poor quality or if the foal was delivered into a bacteria-laden environment.

Antibodies in Colostrum

In the final month of gestation, a mare concentrates antibodies in her milk, but she can only produce antibodies against disease and bacteria to which she has been exposed either through vaccination or environment. The mare’s age and breed are also factors. Maiden mares might produce less colostrum – sometimes only one liter – but it is usually more concentrated with antibodies than the 2 liters typically produced by older mares.

The Effects of Moving a Mare

According to Dr. LeBlanc, a common mistake of mare owners is shipping a mare to a foaling facility within a week of her due date.

“A mare will not have enough time to make antibodies (against) the bacteria in that environment if it is a different type of bacteria that what was in the environment from where she came,” Dr. LeBlanc says. “When the foal is born, if it encounters a bacteria for which his mother has not developed resistance, its immune system will not be equipped to fight it off.”

Dr. LeBlanc says moving a mare from a broodmare band to the foaling barn on the premises is not likely to cause problems, but she emphasized that the foaling barn must be clean.

“It’s not only the amount of antibody she makes, it’s also the amount of challenge from the environment,” she says. “If a mare foals in a dirty foaling stall, the first thing a foal does when it tries to stand is rub its face and mouth in manure. When it licks that manure off, bacteria enters the gastrointestinal tract.”

Colostrometer: Measuring Antibody Content

Dr. LeBlanc developed and patented the colostrometer, a device used to measure the antibody content in a mare’s first milk. Five milliliters of colostrum are deposited in a chamber of the colostrometer to measure the milk’s specific gravity. Specific gravity increases proportionately with the serum antibody level and the concentration of immunoglobulin G (IgG).

“Mares over the age of 14 tend to have lower specific gravity and, therefore, less antibody in the colostrum than younger mares,” Dr. LeBlanc says. “Not all of them, but a good portion of them. Those mares need to be tested as soon after foaling as possible. If they have problems, then hopefully there is colostrum in a colostrum bank available.

“Colostrum should be tested as soon as the mare foals, because once the foal sucks, the specific gravity of the colostrum drops very quickly,” she says, citing the study she conducted at the University of Florida College of Veterinary Medicine that found that normal foals typically consume 75 percent of a mare’s colostrum in the first eight hours they nurse – and all of it within the first 12 hours.

Dr. LeBlanc says that although it might seem prudent to test colostrum before the mare foals (to allow time to obtain plasma or frozen colostrum and notify your veterinarian of potential problems), readings taken at this time are not an accurate predictor.

“If you are concerned about an older mare, it might help,” she says. “In our study, we were very surprised that, from the beginning of the first-stage labor until the foal is delivered at the end of second-stage labor, the antibody level continued to concentrate. It might be borderline before foaling, but after foaling, it concentrates even more. Basically, what is happening is that the water is just leaving her bag.”

Dr. LeBlanc is unsure why this happens, but she theorizes that the effects of oxytocin, a hormone associated with foaling, somehow causes some of the milk’s water content to leave the udder.

1-2-3 Rule and Foal Milk Requirements

Remember the 1-2-3 rule after foaling: The foal should stand within one hour and nurse within two hours; and the mare should pass the placenta within three hours.

We've known for years that foals should ingest roughly 2 quarts of colostrum during the first three hours of life to ensure maximum antibody transfer and protection.

“If the foal is not up and standing by two hours and actively sucking, you need to get colostrum into him,” Dr. LeBlanc says. “Milk the mare and put a stomach tube down the foal, which, in most cases the veterinarian would have to do, and get at least 500 milliliters in the foal.”

She suggests feeding colostrum by stomach tube because, in some cases, bottle feeding will not get adequate colostrum into the foal.

“If the foal is weak, it is not going to suck, and the big thing is to get the colostrum in because what the gut absorbs in that first 18 hours is not specific for antibodies,” Dr. LeBlanc says. “Think of the gut as having an opening, and whatever gets in, gets in. If the foal is born and gets a mouth full of feces, he will absorb all of that bacteria, and as soon as the gut absorbs something – and we call those ‘somethings’ macromolecules, which are either bacteria or antibodies – it closes. On the other hand, if nothing gets in, the foal’s gut closes in 18 to 24 hours. So it is real important that they get colostrum in before they get bacteria in their mouths.”

Benefits of Bathing a Mare Before Foaling

A recent study suggests that mares should be bathed before foaling to eliminate as much bacteria from a newborn foal’s environment as possible. Dr. LeBlanc points out that while this might be a good idea, mare owners should use common sense.

“For instance, let’s say we’re in Florida, and the mare is foaling in May and it’s 90 degrees F,” she says. “(The mare) has run around in the pasture, and sweat is dripping off her body. The sweat, of course, is going to have bacteria in it, and it is going to run down her udder. It would be important to rinse that mare off. But if you are in Kentucky or Michigan, it’s not the best thing for the mare if she is foaling early in the year, it’s cold, and she won’t dry off well because she has a winter coat.

“The udder should be clean and dry so that, when the foal goes to the udder, he is not sucking in bacteria,” she says. “Just take warm water and rinse it down with cotton. If (the mare) has oily smegma between the two halves of the udder, then use soap, rinse it and towel dry it. See to it that the mare is brushed down well and not covered with manure. When the foal gets up and tries to find the udder, they start sucking on their mother in many places. If she has manure stains on her, the foal starts sucking on that manure.”

IgG Levels: Blood Tests for Foals

A blood test to evaluate the foal’s serum antibody level (IgG) is recommended in the first 12 to 24 hours after birth. Antibody or IgG levels should measure a minimum 800 mgs. A healthy foal delivered by uncomplicated birth into a clean environment may be able to fight off disease with IgG levels between 400 and 800 milligrams, but a veterinarian should monitor the foal’s condition closely. Foals with IgG levels between 200 and 400 milligrams are considered to have partial failure and have a 50 percent chance of becoming ill; foals with less than 200 milligrams have complete failure of passive transfer and have a 75 percent chance of illness.

Dangers of Mares That Drip Milk

Failure of passive transfer can develop for a number of reasons. The mare might not produce adequate quantities of colostrum. This is especially true in mares older than 15 years of age or on fescue pastures. The mare also can drip milk for a few days prior to foaling and deplete her store of colostrum.

Mares that drip milk (premature lactation) for more than 24 hours pre-foaling will seldom provide the foal with adequate levels of colostrum. Foals can also suffer from FPT if they fail to nurse, are premature or suffer from disease. Fortunately, there are a number of instruments and tests your veterinarian can use to determine if the mare's colostrum is of good quality and contains adequate amounts of antibodies.

Colostrum Supplements and Banks

When passive transfer fails, quick response is needed to get colostrum or plasma into the foal to bump up IgG levels before the gut closes. Areas where the horse industry is prominent typically have colostrum banks that can supply frozen colostrum, but when the real stuff is not available, commercially available plasma is the next best thing. Plasma comes in two forms: oral and intravenous. But which is better?

“In those types of situations, if the foal is worth some money, I’d do both,” Dr. LeBlanc says. “I’d do the oral within the first six to eight hours of life, then measure the antibody levels at 18-24 hours of life, and if it is not at least 800 milligrams, then I would go ahead and give it intravenous plasma. And I would also put those babies on antibiotics.”

When all is said and done, Mother Nature’s elixir is always the best remedy. So mare owners with more than one foaling mare should consider milking about one cup of colostrum from each mare and freezing it for future use. After the foal first suckles, watch which side the foal sucks from, and then milk colostrum from the other side of the udder and freeze it. It is good for a minimum of three years in a freezer that does not self-defrost.

“We now know that colostrum has various enhancement factors,” says Dr. LeBlanc. “What that means is there are products in colostrum that haven’t all been identified that increase the absorption of antibodies and also stimulate the immune system. From the work of many people, it appears that those factors are not in intravenous or oral plasma products.”

Additional Resources for Mare and Foal Owners

Stages of Labor in Mares: The American Association of Equine Practitioners explains the three stages of your mare's labor.

Mare and Foal Care After Foaling: Give your foals a healthy start: indoor vs. outdoor foaling, foaling supplies checklist, mare and foal care and behavior after foaling, and taking temperatures.

Premature Horse Birth: Preemie Foals: Your foal was born prematurely. Now what? A veterinarian explains common issues caused by premature foaling, prognosis and care.

Foal Growth: Strive for Balance: Genetics, management and environment play significant roles in foal growth. A foal’s growth and development can also be influenced by nutrition.