Three-Day event horses performing the short format endurance portion of an event and horses completing the conventional long format experience a similar amount of stress, according to a recent study. The public has speculated on whether or not horses were adversely or positively affected by the short format since it was introduced to events in 2004 as the long format is being phased out.

Ellen Singer, DVM, DVSc, Dipl. ACVS, ECVS, of England’s University of Liverpool, presented research on the topic on April 29 at the Rolex Kentucky Three-Day Event in Lexington. The research was funded by  British Eventing and was carried out by Singer and Jane Murray, MSc, PhD.

The traditional long format includes four phases of endurance: Phase A–Roads and tracks (walking and trotting); Phase B– Steeplechase (galloping over about eight steeplechase fences); Phase C–Roads and Tracks (walk and trot as a cool down); and Phase D, cross country. Short format horses only perform the Phase D.

In the study, two groups of horses competed in long (53 horses) and short format (69 horses) divisions at one event (Weston Park International Three Day Event CCI** in Shropshire, England). Prior to the event, competitors completed questionnaires about the horse’s fitness level, and experience, on a voluntary basis.

A research team of took the temperature, pulse, and respiration rates of horses at rest before cross country, and at specified increments after completion of Phase D. Additionally, screeners checked the horses for blood gas levels (how gases are being exchanged), blood lactate (lactic acid accumulation to estimate fatigue), electrolytes, and packed cell volume (PCV, the percentage of  red blood cells in the blood ). Muscle enzymes were examined to see how horses recovered from their efforts.

Common reasons for entering the short format were that the rider felt the horse didn&