Identification of environmental factors affecting the speed of purebred Arabian racehorses in The Netherlands

The aim of our study was to identify environmental factors affecting the speed of purebred Arabian racehorses in The Netherlands. Data contained 380 records on 88 purebred Arabian racehorses of varying age and sex. Data were collected from March 2005 through June 2006 during 52 races of varying distance at the Dutch racetrack Duindigt. Because only racing time of the winner was recorded, speed of other horses was derived from the distances these horses covered on the racetrack in the racing time of the winner. Speed increased with the age of the horses and tended to decline in 7-, 8-, and 9-year-old horses. Speed decreased when the distance of a race increased. Compared to speed without competition between horses, speed of horses was higher when one or two competing horses were within one horse length distance for each horse at the moment the winner finishes. For a clear and unbiased estimate of the horse's performance, e.g. breeding value, it seems necessary to correct for competition effects.