Placentitis and Foals' Athletic Prognosis

Editor's Note: This article is part of TheHorse.com's ongoing coverage of the 14th Hagyard Bluegrass Equine Symposium, held Nov. 1-4 in Lexington, Ky.


Placentitis, which often is caused by an ascending infection that enters the mare's uterus through the cervix, is the single most important cause of premature delivery of a foal. Placentitis accounts for nearly one-third of late-term abortions and fetal mortality in the first day of life, and typically costs thousands of dollars to treat each case ($2,000 to $10,000 per case, a previous study estimated).

Some breeders might wonder if treating placentitis is worth the expense said Ed Squires, PhD, Dipl. ACT (hon.), or whether the foal will have decreased athletic potential and, thus, decreased value. At the 2012 Hagyard Bluegrass Equine Symposium, held Nov. 1-4 in Lexington, Ky., Squires, director of University of Kentucky (UK) Ag Equine Programs and executive director of the UK Gluck Equine Research Foundation, presented research examining whether or not foals' athletic potential is affected by placentitis.

Previous studies on the topic have yielded contrasting results, Squires said, so he and his MS student, Sydney Hughes, set out to evaluate the performance of foals from mares suspected of having or being treated for placentitis.

Squires and Hughes evaluated foaling and racing records Thoroughbred foals born on Central Kentucky farms from 2000 to 2008. They paired each suspected placentitis mare with matched control (ideally, those foals would have the same sire and same broodmare sire) from the same farm. In total, they evaluated 190 matched pairs.

The team evaluated foal race records through 2012 and evaluated the number of starts; wins, places, and shows; amount earned; and percentage of black-type winners (i.e., those that won at the highest racing level) from each group.

Key findings of the study included:

  • The majority of mares had subclinical signs of placentitis;
  • Mares' treatment started at, on average, Day 272 of gestation;
  • There were no significant differences in the number of starts; wins, places, and shows; or amount earned between horses from suspect placentitis and controls case as 2-year-olds;
  • Coincidentally, only one 2-year-old black-type winner from both groups, and it was a foal from a mare treated for placentitis;
  • There were no significant differences in the number of starts; wins, places, and shows; or amount earned between horses form suspect placentitis case and control as 3-year-olds and up; and
  • There were more black-type winners from the control group than the case group as 3-year-olds and up.

Squires did note that a confirmation of placentits wasn't available in all cases, and some farms had different degrees of record keeping. However, Squires concluded, "The bottom line is that it seems like it was worth treating these mares. The foals that were born developed into equal performance horses."

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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