by Leslie Huber, D.V.M.
Equine Research Centre
Guelph, Ontario, Canada

All foals require colostrum or “first milk” for protection against disease. You may need an immediate source of colostrum for supplementation in situations such as the following:

  • weak foal
  • twins
  • incompatible blood types (NI)
  • pre-lactation
  • older mare
  • mare death

“First Milk” Protection

Immunoglobulins are antibodies providing protection against disease. In late gestation (pregnancy), antibodies from the mare’s blood are concentrated in her mammary gland. Colostrum or the “first milk” has a high content of these antibodies or immunoglobulins. For approximately 12 hours post foaling, the newborn can absorb these antibodies through the intestinal wall. Immunoglobulin G (IgG) protects the foal from disease.

Colostrum for banking (collection and use at another time) should be collected from the mare within 4-6 hours of foaling. If mares pre-lactate, their colostrum may not contain sufficient IgG. This mare’s colostrum should be checked before banking. On the farm, you can use a colostrometer (modified hydrometer) to estimate the IgG concentration. The specific gravity should be greater than 1.06. For exact concentrations of IgG, samples must be submitted to a laboratory.

An ideal concentration is 50 grams per litre.

Failure of Passive Transfer (FPT)

If a foal does not receive colostrum and immunoglobulins (IgG) in sufficient volume, concentration or shortly after birth, then FPT can occur. FPT means that the level of IgG in the foal’s blood is less than 200 mg/dl. and there is less temporary protection against disease. The risk for developing an infection is greater.

There are test kits available that can be used to determine foal IgG levels. Contact your veterinarian for details. To evaluate the success of passive transfer, measure foal serum levels 15-18 hours after the foal has had its first drink. This allows for sufficient time for the IgG to be absorbed. If the IgG is less than 8g/dl and the foal does not seem “normal” then plasma therapy may be required. Otherwise, a postsucking IgG greater than 4 g/dl should be adequate.

Foals that are less than 18 hours old may still be able to absorb IgG therefore colostrum from a bank or a commercial IgG product could be given orally. Other immune products can be administered IV by your veterinarian.

Collection and Storage

  • Use a clean plastic or glass container – not metal
  • Wash the udder
  • Wash hands
  • Milk from both sides of the udder
  • Collect within 4-6 hours post foaling
  • Filter colostrum through new cheesecloth
  • Check sample for IgG concentration and antibodies
  • Label with date, breed, volume, mare ID and IgG and NI status
  • Store in plastic bags in a chest freezer
  • Thaw at room temperature – Do Not Microwave
  • Frozen colostrum can be stored for 2 years

Neonatal Isoerythrolysis (NI)

This is a condition in a newborn foal that results in destruction of the foal’s red blood cells (RBC’s) resulting in jaundice, anemia and possible death. For NI to occur, the stallion and mare must have incompatible blood types and the foal must inherit the sire’s blood factors. During gestation or at parturition, the mare could be exposed to these factors. She then produces antibodies that appear in the colostrum and will destroy the foals’s RBC’s. The NI condition usually appears with the second or subsequent pregnancies.

NI potential can be determined by:

  • blood typing the mare and stallion for compatability
  • jaundice foal agglutination test at time of foaling—checking compatability of mare’s milk and foal’s blood
  • if incompatible, prevent nursing and feed a milk substitute with commercial globulin or colostrum from a nurse mare or bank—this should be cross-matched for NI antibodies
  • in the last month of gestation, the mare’s serum can be tested for antibody levels
  • approximately 9 days post-foaling mare serum can be checked to determine if the mare has been sensitized to the stallion’s blood type


A foal should receive or be given 400 mls to a litre of colostrum within 4 – 12 hours of foaling.

For orphan or foals needing nutritional support, nurse mares, commercial milk replacers, homemade recipes and other species milk can be used. It is always wise to have some frozen colostrum available for emergency situations. Have telephone numbers for nurse mares and colostrum bank sources readily at hand.

Of course, it is preferable to supply the newborn with its own species’ milk since the composition of milks from different animals vary. The first choice is finding a nurse mare. If this is not possible then purchase a commercial milk replacer that is specifically made for the horse. These products are available either from your veterinarian or feed store.

In an emergency, milk from another species can be used temporarily. Goat’s milk is similar in protein and fat content but is about ½ the lactose. Cow’s colostrum will not meet the needs of the newborn foal since bovine IgG does not live long in the foal. Unaltered cow’s milk differs in protein, fat and lactose content. If used, the fat and protein content needs to be reduced and the lactose increased.

Examples of homemade formulas:

1 pint (568 mls) 2% cow’s milk
4 oz limewater
1.5 teaspoons corn syrup


3 pints 2% cow’s milk 1 pint water ¼ package Sure-Jell pectin

When feeding any milk substitute, the foal’s health status and growth rate (for that breed) must be monitored frequently.