Cytogenetics and Molecular Diagnosis in Horse Infertility

Abstract

As the popularity of horse breeding stays steady, many breeders and owners send their horses samples to cytogenetics analysis for signs of infertility or other genetic abnormalities. Here, we report three cases of horses that were subjected to chromosome analysis due to infertility issues. Unfortunately, in the case of the H304 mare, the horse has a normal 64, XX female karyotype and no chromosomal abnormality was observed to explain the infertile issue. In the case of the H305 mare, the horse has a 64, XY male karyotype which indicates genetically male and no sign of chromosomal abnormality under cytogenetic analysis. However, PCR analysis indicates the loss of the SRY in the Y chromosome. This is a typical male to female sex reversal and one of the most common genetic sex abnormalities in horses. In the H306 mare, the horse has only one X chromosome; 63, XO, called X monosomy. This is the most common sex chromosomal abnormality in horses. The combination of clinical cytogenetic analysis and the use of PCR are the strongest tool to determine the chromosomal abnormality in the equine industry and the case H305 is a good example to support how these two different approaches compensate each other to generate a reliable diagnosis. Determination of genetic abnormalities using two techniques will help horse breeders and equine practitioners to make the most informed decisions about breeding plans.