Researchers Confirm IgG Values for Predicting Foal Survival
Foals are born without infection-fighting proteins called antibodies (or immunoglobulin G %91IgG%93) circulating in the blood stream. | Photo: Anne M. Eberhardt/The Horse
It’s foaling season again, which means it’s also time to watch newborns for signs of failure of passive transfer. This condition occurs when the foal does not ingest or absorb a sufficient quantity or quality of colostrum (the mare’s first milk), which results in a reduced ability to fight disease.

Foals are born without infection-fighting proteins called antibodies (or immunoglobulin G ) circulating in the blood stream. The mare’s colostrum contains these IgGs and other immunoglobulins to help protect foals from developing life-threatening infections. But how do you know if your foal has obtained enough IgG?

“Even though veterinarians and horse owners and managers have been testing foals for failure of passive transfer (FPT) by measuring foal IgG levels for over 30 years, the accepted ‘cut-off value’ for what defines FPT remains largely empirical,” explained Ramiro Toribio, DVM, MS, PhD, Dipl. ACVIM, from the Ohio State University College of Veterinary Medicine, in Columbus.

Reported values vary dramatically, especially when classifying foals with adequate transfer of passive immunity versus partial or complete. Overall, however, past study results have suggested that the “magic” IgG level is 800 mg/dL

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