Blood and serum testing can provide a wealth of information about a horse’s current health status. Is he battling an infection or an immune-mediated disease? Does he have metabolic issues? Liver or kidney damage?

These red blood cell, white blood cell, platelet, and other levels become less clear, however, when dealing with a neonatal foal, whose body is still adapting to life outside the uterus. Therefore, it’s important that veterinarians become familiar with what’s normal and what’s not normal on a foal’s blood sample test results.

“Most labs only report reference ranges for adult horses, which can lead to foal samples being incorrectly flagged as abnormal,” said Michelle Barton, DVM, PhD, Dipl. ACVIM, director of clinical academic affairs and the Fuller E. Callaway endowed professor of large animal medicine at the University of Georgia College of Veterinary Medicine’s Department of Large Animal Medicine.

She described these differences between foals and adult horses at the 2015 American Association of Equine Practitioner’s Convention, held Dec. 5-9 in Las Vegas, covering everything from red and white blood cells to kidney and liver values.

Red blood cells Immediately after birth, a foal’s red blood cell count is about the same or slightly higher than an adult’s, thanks to the last little bit of blood the dam’s placenta transfers, said Barton. Within 48 hours, as the foal begins consuming colostrum, or first milk, the count drops and continues to decrease gradually over th