Clinical Applications of Preimplantation Genetic Testing in Equine, Bovine, and Human Embryos

• Preimplantation genetic testing is used in human medicine.
• Preimplantation genetic testing is used in animal production.
• Preimplantation genetic testing detects aneuploidies, genetic disorders, and valuable phenotypes.
• Preimplantation genetic testing helps to decide which embryos should be transferred.
• Single nucleotide polymorphism microarrays have broadened the application of preimplantation genetic testing.

The use of preimplantation genetic testing (PGT) in reproductive medicine and animal production has increased significantly in the last few years. Preimplantation genetic testing starts with the collection of a few cells from the embryo and continues with the genetic analysis of the DNA in the sample. The last step is the interpretation of the results and the decision whether to transfer the embryo or not. New genetic tools have broadened the application of PGT. In humans, preimplantation genetic diagnosis helps select against embryos carrying known genetic disorders, and preimplantation genetic screening is used to help prevent the transfer of embryos with aneuploidies. In cattle, PGT is increasingly used to select embryos carrying genetic traits of interest for meat or milk production. The availability of single nucleotide polymorphism (SNP) microarray chips at a low cost has helped the incorporation of this technology in genetic selection programs. In the horse, embryos have been mainly analyzed for sex selection and for the detection of known genetic disorders. Recently, chips with up to 600K SNPs have become commercially available for horses. This technology, in combination with the recent success of embryo cryopreservation, will probably lead to the inclusion of PGT as a tool for horse breeding in the future.