Foals are born with no immunity to protect them against infection. All foals acquire immunity through ‘passive transfer’ of antibodies from the mare’s first milk, called colostrum.

Antibodies are proteins in the body that fight off infectious disease organisms, such as bacteria and viruses.

If the foal doesn’t get any or enough quality colostrum in the first 12 hours of life, he will not be protected against harmful bacteria and viruses. This is referred to as ‘failure of passive transfer’ or FPT.

 4 – 6 weeks before foaling

• Vaccinate the mare – this makes sure that she has developed antibodies to give to the foal via colostrum
• The placenta in horses does not allow antibodies to cross to the foal

• Ensure that the mare’s udder is filling with milk
• Don’t touch the teats
• If the mare is running milk, she will probably be losing the high-quality colostrum the foal needs. In this case, the foal need to be tested for FPT.

 At birth

• Check that the foal is standing and drinking
• If you have the correct equipment, you can check the IgG (antibody) level in the colostrum. This verifies that the mare’s colostrum is high quality.

 6 – 12 hours after foaling

• The foal must consume at least 1-3 litres of high quality colostrum
• 85% of antibodies are absorbed in the first 6-8 hours

 12 hours after foaling

• Colostrum absorption across the foal’s gut reduces

 24 hours after foaling

• The foal’s small intestine can no longer absorb antibodies
• Drinking colostrum past this point will not increase immunity

 It is vitally important to call your vet if you think your foal has not had enough quality colostrum.

Your vet will measure your foal’s antibody level:

<2g/L  = total FPT

2-8g/L = partial FPT

>8g/L = successful passive transfer

Around 5-20% of foals have FPT. There are many causes, of which the most common are:

• Early lactation
• Placental infections
• Delay in standing and drinking
• Premature birth
• Poor-quality colostrum
• Fescue toxicosis

How is FPT corrected?

Foals with low antibody levels are at a much higher risk of developing life-threatening infections. Many FPT foals develop multiple illnesses which, if they survive, often still affect them into adulthood.

So, it is incredibly important to check for FPT and treat the foal early, before infections can arise.

Your vet will most likely recommend intravenous plasma (after 24 hours). If caught early (before 24 hours), fresh or frozen colostrum from another mare or commercial formula may be given.