A newborn foal cannot mount an immune response to any diseases commonly found in the environment. Without this ability to fight, the foal dies. To prevent this, the mother produces molecules that effectively attack any challenge the foal might have in the first 30 to 60 days of life. After this time, foals can make their own defense molecules.

The problem lies in how the mare gets this protection to the foal. This protection transfer is passive from the mare through the first milk produced after birth (colostrum). During the first 24 hours of life, the gut lining of the foal allows these very large protective molecules through so the body can absorb and use them. However, after this time, the gut lining “closes,” and the large molecules can no longer pass into the body.

There are four ways the transfer of defense molecules can not get into the foal and offer their protection:

• The mare leaks out all the colostrum before birth.
• The colostrum is not made with enough protection.
• The foal can’t drink the colostrum (sick or injured).
• The foal doesn’t drink the colostrum within the time before gut closure.

In any of these cases, the result is the failure of passive transfer of the needed protective molecules. The only solution is to administer the colostrum via a nasogastric tube (if before gut closure) or by intravenous injection (if after gut closure) of harvested serum (commercially available).

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