Genetic parameters of performance traits in horse endurance races

The objective of the study was to find a heritable trait measuring ability in endurance races from competition results in order to select endurance horses from them. The results of 90–160 km endurance races in France from 2002 to 2004 were available including 2795 horses, 3.2 races per horse, from which 2264 had a speed measured, i.e. 5252 measurements of speed and 9059 of placing (0 or 1 when the horse completed the race). The model included fixed effects of sex, age, month of birth (not significant), region of birth, breed, and random effects of permanent environmental effects and animal effect (20,854 horses). Heritabilities were 0.28 and 0.06 (0.10 on underlying scale) respectively for speed and placing. Repeatabilities were respectively 0.44 and 0.07 (0.12). The genetic correlation was 0.87. No genetic differences were found between the results in small distance races (90 km) and long distance races (120–160 km). Additional data on young horses in specific races (20–60 km) with controlled speed did not give a precocious criterion (genetic correlation between speed in adult races and maximum level of distance and difficulty in the young horse equal to 0.07) for selection. In conclusion, breeding values should be calculated from speed and placing in races ≥ 90 km. A higher genetic progress is expected than for other equestrian disciplines since heritability is considerably higher for a trait measured in a single event.