by Emily Dickson

Failure of Passive Transfer in Foals

Failure of Passive Transfer in Foals

Published: July 2020 | Updated: January 2023

Given world events the last few years, most of us are very familiar with using the word antibody, but do we know exactly what that word means and why we should care so much? 

Understanding antibodies is a critical component to new foal care, as foals enter the world with a naive immune system, vulnerable to pathogens. 

So What is An Antibody? 

An antibody is a protein produced by the immune system, designed to attach to specific antigens, or foreign substances, and remove them from the body. 

To break down the word even further: An antibody helps remove the bad things in the “body” that are “anti” health. 

Immunoglobulin is another word for antibody

Antibodies, or immunoglobulins, are classified based on their structure. There are 5 main classes:

  1. Immunoglobulin G (IgG)
  2. Immunoglobulin E (IgE)
  3. Immunoglobulin M (IgM)
  4. Immunoglobulin D (IgD)
  5. Immunoglobulin A (IgA)

As horses (and humans!) are exposed to more pathogens throughout life, their immune system gets smarter and remembers the bad guys. This is how we develop immunity and the ability to produce the necessary antibodies when needed so we do not get sick upon exposure to the same pathogen. This is the whole premise behind vaccinations. By imitating an infection and exposing the body to antigens, the body can create antibodies (or protection) before a virus enters and wreaks havoc.   

What is Foal Failure of Passive Transfer?

Human babies are born with some antibodies (and therefore immunity) that they acquired from their mom via the placenta while in the womb. These antibodies stay active for the first few weeks of life while the baby’s immune system develops and responds to the world. 

Foals do not have this luxury. Newborn foals enter the world with a functioning immune system, but no antibody protection, which means they are more vulnerable to infection in the first few weeks of life. Particularly, in the first few days, foals are completely reliant on the antibodies present in their mom’s colostrum, or first milk. 

A newborn foal has temporary specialized cells in their small intestine which are capable of absorbing the large immunoglobulins present in colostrum. These cells are especially active in the first 6-8 hours after birth. Each hour counts, as absorption completely stops (“gut closure”) at 24-36 hours of life.  

Failure of passive transfer (FPT) is what happens if the foal does not absorb high enough levels of antibodies from the mare’s colostrum. Foal FPT is thought to occur in up to 25% of newborn foals. 

How Do You Check a Foal for Colostrum Intake? 

An IgG test in foals tests for levels of immunoglobulin G, the antibodies consumed from colostrum. There are various antibody testing options, but one of the more common IgG tests is the foal snap test, because it is an easy (just requires a blood draw), stall-side way to make sure that the foal is getting a sufficient amount of critical protection from their mama.  

Protocols on when to use the snap foal IgG test vary, but many veterinarians test around 12 hours of age, because this allows time for intervention if absorption is not going well. The general rule of thumb is that if IgG levels are below 400 mg/dL, your foal needs to be supplemented with frozen colostrum which has been thawed or a colostrum replacement.

Talk to your vet before your foal arrives and make sure you have a plan in place for the day of foaling. Your vet is a crucial piece of this process and in setting your newborn foal up for success. 

What Can a Horseman Do to Avoid FPT in Their Foals? 

When your foal is born, make sure to follow the 1,2,3 timeline and test your foal for IgG levels around 12 hours of life. 

In addition, Fullbucket created a product called Foal Kick Start, which is designed for use on day 1 of a newborn foal’s life. 

Foal Kick Start contains an ingredient called dried egg product, which contains antibodies against 6 of the most common diseases that foals are at risk for contracting in their first hours and days. 

All you have to do is give one-half of the tube at birth and the other half of the tube at 6-8 hours of life for optimal immune support and protection.

As always, work with your veterinarian every step of the way when it comes to new foal care. The first week of the foal’s life is CRITICAL, so set them up for success by having a plan, working with professionals and supporting their immune system

Read More:

Failure of Passive Transfer in Horses

Failure of Passive Transfer: Early Testing is Key

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