Effect of a horse's month of birth on its future sport performance. I. Effect on annual phenotypic indices

Abstract

This study examined the effect of month of birth on performance in flat races, steeplechase and hurdle races, harness racing, and equestrian competitions (jumping, 3-day events, dressage). The performance was evaluated by considering the annual phenotypic indices calculated from their earnings and published by the SIRE (Système d'Identification Répertoriant les Equidés): ICP for flat races, ICO for the steeplechases and hurdle races, ITR for trotting races, ISO for jumping, ICC for the Olympic 3-day event and ICD for dressage. The effect of month of birth was tested through variance analysis and was significant in every case. Horses that are born early in the year had an advantage and performed better than horses born later. The effect varied in magnitude with the different disciplines. It was marked in flat races and trotting races, and lower in the steeplechases and Olympic sport disciplines. The effect decreased with age, but remained significant very late in a horse's career. In conclusion, an early birth month is advantageous for a horse and application of winter lighting protocols for mares should take this into consideration. Because of its statistical significance, this effect should be routinely taken into account in breeding value estimation, particularly for racing activities.