02509naa a2200289 a 450000100080000000500110000800800410001902400540006010000190011424501780013326000090031130000110032049000070033152016290033865000110196765000120197865000170199065300190200765300080202670000190203470000170205370000260207070000230209670000230211970000160214277300610215820551002018-11-07       2016    bl uuuu     u00u1 u    #d7 ahttp://dx.doi.org/10.1016/j.jevs.2015.07.0012DOI1 aPEREIRA, G. L.  aComparison of sequence variants in the PDK4 and COX4I2 genes between racing and cutting lines of quarter horses and associations with the speed index.h[electronic resource]  c2016  a1-6 39  v39  aDifferent selection objectives within the Quarter Horse breed led to the formation of groups with distinct skills, including the racing and cutting lines. With a smaller population size in Brazil, but of great economic representativeness, the racing line is characterized by animals that can reach high speeds over short distances and within a short period of time. The cutting line is destined for functional tests, exploring skills such as agility and obedience. Although the athletic performance of horses is likely to be influenced by a large number of genes, few genetic variants have so far been related to this trait and this was done exclusively in Thoroughbreds, including the g.38973231G&gtA singlenucleotide polymorphism in the PDK4 gene and the g.22684390C&gtT single-nucleotide polymorphism in the COX4I2 gene. The results of the present study demonstrate the presence of polymorphic PDK4 and COX4I2 genes in Quarter Horses. The analysis of 296 racing animals and 68 cutting animals revealed significant differences in allele and genotype frequencies between the two lines. The same was not observed when these frequencies were compared between extreme racing performance phenotypes. There were also no significant associations between alleles of the two polymorphisms and the speed index. These results suggest that the alleles of the PDK4 and COX4I2 genes, which are related to better racecourse performance in Thoroughbreds, are probably associated with beneficial adaptations in aerobic metabolism and therefore play secondary roles in sprint racing performance in Quarter Horses, which is mainly anaerobic.  aHorses  aEqüino  aPolimorfismo  aGene candidato  aQTL1 aMATTEIS, R. de1 aMEIRA, C. T.1 aREGITANO, L. C. de A.1 aSILVA, J. A. II V.1 aCHARDULO, L. A. L.1 aCURI, R. A.  tJournal of Equine Veterinary Sciencegv.39, p.1-6, 2016.