Study Examines EIPH and Racing Performance

A study published online this spring found no link between the vast majority of horses who suffer from exercise-induced pulmonary hemorrhage and long-term racing performance although the study did find that the small percentage of horses who suffer severe EIPH see their long-term performance impaired.

Published May 29, the study was conducted by some of the world's foremost experts on EIPH, including Kenneth Hinchcliff and Paul Morley. Hinchcliff and Morley were two of the authors of a landmark 2009 study that concluded pre-race administration of furosemide (Salix, commonly called Lasix) decreased the incidence and severity of EIPH. (Jockey Club: Study Shows Lasix Not Needed)

That study examined horses racing in South Africa in races carded for the study. In this latest study, Hinchcliff, Morley, S.L. Sullivan, and G.A. Anderson acknowledged EIPH can impair short-term race performance but examined the relationship between EIPH detected on a single occasion and long-term athletic performance in Thoroughbred racehorses.

In the study, 744 Thoroughbreds in Australia underwent a single tracheobronchoscopic examination to determine presence and severity of EIPH in 2003. The study then kept tabs on the racing performance of each of these horses.

Following retirement of all the study horses from racing, career performance data, including duration, earnings, starts, wins, and placings, were abstracted from a commercial database. The association between presence and severity of EIPH in the single tracheobronchoscopic exam and individual performance variables were analyzed.

In the tracheobronschocopic exams, 45% of the horses showed no EIPH while 55% of the horses showed some level of EIPH, which is broken down into four grade levels of severity. Grade 4 is the most severe level, typically associated with epistaxis (bleeding from the nostrils). Only 1.7% of the examined horses showed this level of EIPH. 

There were 273 horses found at grade I EIPH (36.7% of all horses examined), 101 at grade 2 (13.6%), and 25 at grade 3 (3.4%).

The study found no association between low levels of EIPH, grade I, 2, and 3, and long-term racing performance. The racing performance of horses examined who showed grade 4 EIPH was impacted, suggesting "that the severity of EIPH commoly associated with epistaxis adversely affects either the horse's opportunity to race or physiologic capacity to race."

The study concluded, "There is no association between EIPH grades 0 (no EIPH), 1, 2, and 3 and long-term racing performance."

The study noted that this conclusion was based on a single endoscopic evaluation. It suggested more study is needed on why horses with grade 4 EIPH see their long-term performance suffer.