Analysis of Genetic Variability in the Argentine Polo Horse With a Panel of Microsatellite Markers

Argentine Polo (AP) is a young horse breed with a fast expansion because of an open registry policy and the application of assisted reproduction technologies. In the last years, AP showed a remarkable progress associated with the use of embryo transfer technology and intensive selection based on sport performance. However, these practices could have affected the genetic variability of the breed. To monitor these potential changes, a parentage panel of 11-15 microsatellites was investigated for changes in allele frequencies, heterozygosity, and exclusion probability over a 16 year period. Frequency of 36 alleles in 13 markers showed significant departures from expected changes because of random genetic drift. Six markers showed both allelic frequency increase and expected heterozygosity (He) reduction, suggesting the influence of selective breeding or hitchhiking effects. The average He decreased significantly although was lower than the observed heterozygosity, indicating a still low inbreeding level. Although the exclusion probability of the panel showed a trend to decrease, it is over 0.9995, the recommended value for equine parentage exclusion.