By Stacey Oke, DVM, MSc • May 04, 2015 • Article #35733 from TheHorse.com.
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 [IgG]) 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.
To provide more science to back up that magic, Toribio; Rachel Liepman, DVM; and colleagues collected data from 597 foals 7 days old or younger from three hospitals over six foaling seasons. They then divided those foals into one of three groups: healthy, sick but nonseptic (no bacteria in the bloodstream), and septic.
“Our data suggested that foals with IgG levels lower than 800 mg/dL were, indeed, several times more likely to die compared with foals with IgG levels greater than 800 mg/dL,” regardless of how far under the 800 mg threshold the value was, Toribio said. “Therefore, the traditional value of 800 mg/dL remains valid in predicting survival of hospitalized foals.”
The study authors also found:
- A proportional association between low IgG concentration and foal death; and
- No difference in survival for foals with IgG levels 801-1,200 mg/dL and greater than 1,200 mg/dL.
Toribio warned clinicians, however, that, “foals with adequate passive transfer of immunity can and do still die, highlighting the fact that low IgG is a risk factor for disease and is not by itself a diagnosis.”
The study, “Validation of IgG cut-off values and their association with survival in neonatal foals,” will be published in an upcoming edition of the Equine Veterinary Journal.
Diagnostic tools for determining foal IgG
Find a diagnostic test for your foal at the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL). We offer a radial immunodiffusion test to quantify Immunoglobulin G (IgG) in equine serum. This serologic test is performed at the College Station laboratory.
For more information, click: Immunoglobulin