Breeding evaluation of arab horses from their racing results in Tunisia by a BLUP with an animal model approach

Abstract

The aim of this study was to estimate the breeding value of Arab horses in Tunisia. Racing results (36203) were available corresponding to 2432 horses issued from 811 dams and 218 sires registered in the Tunisian stud book and in the races organized from 1980 to 2001 by the Societe des courses de Tunis. Performance was described by two criteria: the earning and the rank in the race used after some transformations: (i) attribution of theoretical earnings to the not placed horses and normalization by a Log transformation, (ii) normalized rank according to statistical tables on which a rate calculation was applied (see further). The effects of year, age and sex were signif- icant. The effect of weight carried was also significant but the results appeared paradoxical because the more they carried the better were the performances. Variance component estimation using VCE software gave the following values for heritability: 0.09 and 0.12, respectively, for the Log of earning and the ranking value. Repeatability was the following: 0.25 and 0.35, respectively. The maternal en- vironment component was evaluated as 0.04 for the ranking value and 0.03 for the Log of earning. The genetic correlation of the two criteria was estimated to 0.97 standard error and was around 0.01 in all cases. In conclusion, the Log of earning and ranking value are two appropriate manners to take into account racing performance in selection for Arab horses in Tunisia. It can be remarked, however, that the heritability of the ranking value was higher. The adjustment of earnings with the level of races was probably not precise enough and intra race as a function of the ranks, the respect of a constant relative decrease of the earnings according to the place was too approximate. horse / racing ability / purebred Arabian / BLUP / animal model / Tunisia