In vitro production of equine embryos: state of the art.

This research article outlines the procedures and possibilities of producing horse embryos in vitro for research and clinical applications, noting that the rates of success are comparable to those seen in cattle.

Methodology and Procedures

• The article begins by explaining the possible methods of deriving oocytes, which are female gametes necessary for reproduction. These can be obtained post-death from excised ovaries, or collected in life from either immature follicles or stimulated pre-ovulatory follicles within the mare.
• The in vitro maturation (IVM) of these immature oocytes is also detailed. IVM is a common in vitro technique used to develop immature oocytes to the stage where they can successfully be fertilized. The paper indicates a success rate of approximately 60%.

Fertilization Techniques

• The article continues by acknowledging that standard in vitro fertilization (IVF), where the egg and sperm are combined outside the body, is not yet reliable in horses. Therefore, a technique called intracytoplasmic sperm injection (ICSI) is employed instead. ICSI involves the injection of a single sperm directly into the cytoplasm of an egg. This is typically used in cases where IVF would be unlikely to succeed.

Embryo Culture and Pregnancy Rates

• The researchers then describe the requirements for successful embryo culture. The medium in which the fertilized egg is cultured needs to have high concentrations of glucose, particularly during the blastocyst development stage. A blastocyst is an embryo that has developed for around five to six days after fertilization.
• It is noted that the rates of successful blastocyst development are comparable to those seen in cattle (25% to 35%).
• Finally, the article finishes by comparing the pregnancy rates obtained after the transfer of these in vitro-produced blastocysts, to those achieved through natural methods. It states that the chances of success are similar for embryos derived in vitro and those naturally obtained ex vivo (directly from an organism).