-Declarations of matings (535 746) and 308 549 consecutive declarations of birth from 1989 to 1999 were analysed by logistic regression in order to determine the effects of year, breed and age of parents on numerical productivity (the number of foals declared per mated mare per year). For the years 1994 to 1999, the status of the mare, type of mating and month of first mating, were also available. The effect of inbreeding and, for warm-blooded horses, the effect of the level of performances or the effect of the level of breeding value estimation were also analysed. The main results are the following: numerical productivity progressed in France more for draught breeds than for saddle breeds and trotters. Thoroughbreds progressed less and just reached the level of significance. Cold-blooded horses, however, appeared less productive than warm-blooded horses for which thoroughbreds were at the lower level. It cannot be concluded if this figure reveals biological differences in fertility or if it is only the result of differences in managing the official declarations. For warm-blooded horses, the absence of negative relationships between the trends of selection and numerical productivity results appeared clearly. A high performance level for the mare was positively associated with higher productivity results in sport and trotting horses and showed no significant influence for galloping horses. The relationships with breeding value estimation illustrated the same trends.horse / fertility / logistic model / factors of variation / selection / inbreeding

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-The aim of this study was to estimate the breeding value of English Thoroughbreds in the Czech Republic using racing results from a 22-year period . The data include the performance of two and three-year-old horses which raced in flat races at hippodromes in the Czech Republic. The racing results (30 203) were available corresponding to 6 333 horses descending from 762 sires and 2 836 dams. Different criteria were applied in order to analyse the performance: Log of earnings per race, a normalized ranking value, distance of the race when placed, earnings and number of starts for 2, 3, 2+3 year-old horses. After preliminary studies, a year effect or a sex by year effect was finally retained. Variance component estimation using VCE software gave the following values for heritability (±standard errors): 0.14 ± 0.01 and 0.16 ± 0.01 for the Log of earnings per race and the ranking value. Repeatability was 0.31 and 0.35, respectively. The maternal environment component was evaluated as 0.02 ± 0.004 for the Log of earnings per race and 0.03 ± 0.004 for the ranking value. We found that the Log of earnings per race and the ranking value were two appropriate criteria when taking into account racing performance in selection for Thoroughbreds in the Czech Republic. The genetic correlation of the two criteria was 0.98 ± 0.003. The heritability for the distance when placed was 0.18 ± 0.01. The genetic correlation of the Log of earnings per race and distance was medium, 0.38 ± 0.05 and of the same order, 0.39 ± 0.05 for ranking value and distance. In the case where we used the Log of annual earnings and the number of starts, the heritabilities were for the Log of earnings: 0.15 ± 0.03 for two-year-olds, 0.34 ± 0.03 for three-year-olds and 0.32 ± 0.03 for two and three-year-old careers together and respectively, 0.12 ± 0.03, 0.21 ± 0.03 and 0.20 ± 0.02 for number of starts. The genetic correlations between the earnings and the number of starts were respectively: 0.26 ± 0.14, 0.33 ± 0.06 and 0.19 ± 0.07. The genetic correlation between the number of starts for two and three year-olds which was restricted to horses earning money for two consecutive years, was average: 0.35 ± 0.05 and between earnings for the same ages was high 0.80 ± 0.04.

-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 "Société 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 "performance rate" calculation was applied (see further). The effects of year, age and sex were significant. 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 environment 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 Résumé -Évaluation génétique par un BLUP en modèle animal des chevaux arabes d'après leurs résultats en course en Tunisie. L'objectif de l'étude est l'estimation de la valeur génétique additive des chevaux de pur-sang arabe en Tunisie, il est mené sur 36203 données relatives à 2432 chevaux issus de 811 mères et 218 pères de pur-sang arabe enregistrés dans le stud book tunisien et (ii) un classement normalisé d'après les tables statistiques sur lequel une procédure de « performance rate » a été appliquée. Les effets année, âge et sexe s'avèrent significatifs. Pour le poids porté, le résul-tat paraît paradoxal puisque les chevaux les plus chargés expriment en moyenne de meilleures performances. L'analyse par un modèle animal avec répétabilité grâce au logiciel VCE a conduit à l'estimation des paramètres génétiques : une héritabilité de 0,09 ± 0,01 et 0,12 ± 0,01 respectivement pour le log du gain et la valeur classement ; la répétabilité est de 0,25 ± 0,01 pour le log du gain et 0,35 ± 0,01 pour le classement. L'effet maternel est de 0,04 ± 0,01 pour le classement et 0,03 ± 0,01 pour le log du gain. Il ressort alors que le log du gain et la valeur classement sont deux bonnes façons...

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Endurance horses are able to run at more than 20 km/h for 160 km (in bouts of 30–40 km). This level of performance is based on intense aerobic metabolism, effective body heat dissipation and the ability to endure painful exercise. The known heritabilities of endurance performance and exercise-related physiological traits in Arabian horses suggest that adaptation to extreme endurance exercise is influenced by genetic factors. The objective of the present genome-wide association study (GWAS) was to identify single nucleotide polymorphisms (SNPs) related to endurance racing performance in 597 Arabian horses. The performance traits studied were the total race distance, average race speed and finishing status (qualified, eliminated or retired). We used three mixed models that included a fixed allele or genotype effect and a random, polygenic effect. Quantile-quantile plots were acceptable, and the regression coefficients for actual vs. expected log10 p-values ranged from 0.865 to 1.055. The GWAS revealed five significant quantitative trait loci (QTL) corresponding to 6 SNPs on chromosomes 6, 1, 7, 16, and 29 (two SNPs) with corrected p-values from 1.7 × 10−6 to 1.8 × 10−5. Annotation of these 5 QTL revealed two genes: sortilin-related VPS10-domain-containing receptor 3 (SORCS3) on chromosome 1 is involved in protein trafficking, and solute carrier family 39 member 12 (SLC39A12) on chromosome 29 is active in zinc transport and cell homeostasis. These two coding genes could be involved in neuronal tissues (CNS). The other QTL on chromosomes 6, 7, and 16 may be involved in the regulation of the gene expression through non-coding RNAs, CpG islands and transcription factor binding sites. On chromosome 6, a new candidate equine long non-coding RNA (KCNQ1OT1 ortholog: opposite antisense transcript 1 of potassium voltage-gated channel subfamily Q member 1 gene) was predicted in silico and validated by RT-qPCR in primary cultures of equine myoblasts and fibroblasts. This lncRNA could be one element of the cardiac rhythm regulation. Our GWAS revealed that equine performance during endurance races is a complex polygenic trait, and is partially governed by at least 5 QTL: two coding genes involved in neuronal tissues and three other loci with many regulatory functions such as slowing down heart rate.

-This study examines the effect of month of birth and its interactions with sex, age and year of performance for performance in flat races, jumping races (steeple-chases and hurdle races), trotting races, and equestrian competitions (jumping, eventing, dressage). The level of performance was evaluated by considering the logarithm of annual earnings and the logarithm of annual earnings per start in each discipline. Significant interactions were found between age and sex in all racing disciplines and in jumping. In some cases, a significant interaction also appeared between month of birth and sex. This was ignored in our previous study. Taking this factor into account, however, does not change the conclusions of this article very much, although it allows a greater precision of the estimates. For example, the decrease of the effect of month of birth with increasing age is only significant for racing disciplines. This finding supports the idea that the effect of month of birth in racing horses results mainly from real age differences between horses from the same 'administrative' age class. Any lingering effect in horses older than 4 years seems to be stable and of smaller magnitude. For these adult horses the effect of age differences in month is expected to tend to zero