Genetic analysis of racing performance of trotter horses in Spain

Trotting racing is one of the most popular horse sports in Europe. The Spanish Trotter Horse (STH) can be considered as a composite of the main World trotter populations. This is because the Spanish Trotter Breed often imports breeding stock from the main Trotter Horse Breeds; mainly American and French Trotters. The Breeding Program of the STH includes earnings, placing and time traits as main selection criteria. The main aim of this paper is to estimate the genetic parameters in the STH population and to show the characteristics of the STH population as a connecting population in order to include it in an international breeding evaluation for trotting ability. For this purpose, we used 285,538 racing records from 5086 horses during a 16 year period. All the known ancestors of the recorded animals were included in the pedigree file (10,940 horses), making sure that at least four generations for foreign horses were included. A multivariate Animal Model was developed using four different performance traits: annual earnings (log transformed), percentage of first placing in a year (square root transformed), time per kilometer and best racing time per hippodrome and type of start . Genetic connectedness of performance data was adequate. The estimates of heritability ranged between 0.14 ± 0.017 for the percentage of first placing and 0.29 ± 0.018 for the best racing time per hippodrome and type of start . The other traits had a medium magnitude of heritability, and were 0.27 ± 0.018 for the annual earnings and 0.28 ± 0.017 for the annual earnings and the time per kilometer . All these values were within the range with those reported by authors for other trotter populations. The repeatability values had ranged between 0.31 for the percentage of first placing and 0.65 for the time per kilometer . The genetic correlations have medium-high magnitude, ranging between 0.61 ± 0.044 and 0.99 ± 0.005. There was a negative correlation between time traits and the other analyzed traits, as was expected because a decrease in the time traits is always related to an improvement in the performance results in races. Given its own genetic composition, the population of trotter horses in Spain could be considered as a connecting population in order to develop an international genetic evaluation. Therefore, these parameters could be taken into account for an international genetic evaluation of trotter horses.