Blastocyst evaluation by means of differential staining: a practical approach

Techniques for in vitro production of embryos have been developed world-wid e in different species, with promising results in human and ruminants. Thou sands of human IVF-babies have been born during the last 20 years and thous ands of in vitro-produced calves have been born since the late 1980s. With current methods for bovine in vitro fertilization, about 30-40% of in vitro -fertilized bovine oocytes develop further to the blastocyst stage and can be used for transfer. A proper evaluation of blastocyst quality remains how ever, an import ant challenge for every researcher involved in embryology a nd for every clinician who wants to select the best embryos for transfer. T his review attempts to summarize the different methods available for estima tion of blastocyst quality with a special emphasis upon differential staini ng.