Application of preimplantation genetic diagnosis in equine blastocysts

Pre-implantation genetic diagnosis (PGD) is a procedure used to screen in vitroproduced embryos or embryos recovered after uterine flush to determine genetic traits by DNA testing prior to transfer into the uterus. Biopsy methods to obtain a sample of cells for genetic analysis before implantation have been successful in small embryos (morulae and blastocysts < 300 µm diameter), but this technique was initially unsuccessful in large embryos (expanded blastocysts > 300 µm diameter). The successful biopsy of expanded equine blastocysts via micromanipulation, with subsequent normal pregnancy rates, was first reported in 2010. Direct PCR may be performed when evaluating only one gene, such as for embryo sexing, while whole genome amplification is effective for subsequent multiplex PCR of multiple genes