Male Factors Affecting the Success of Equine In Vitro Embryo Production by Ovum Pickup-Intracytoplasmic Sperm Injection in a Clinical Setting

•The success of Assisted reproductive technology is influenced by the male factor.•Individual stallions as well as batches of semen are sources of variation.•The male factor can be confounded with the female factor.•True male factor effect can be detected with appropriate intracytoplasmic sperm injection tests.

There is growing interest of the equine industry in assisted reproductive technologies (ARTs) to treat both male and female infertility or to value individuals of high genetic merit. Ovum pickup and intracytoplasmic sperm injection are the most recent introduced techniques in the equine ART toolbox. We have reviewed in this manuscript the contribution of the male factor to the success of these procedures in a clinical setting, and we have reported some experimental new data. The semen sample used for intracytoplasmic sperm injection (ICSI) is critical for the outcome of the procedure, and many factors including breed, fertility in vivo, method of sperm preparation, and batch play a role. It is not simple to identify these factors in a clinical setting since the variability from the male side is added to that of the donor female. Preliminary tests in vitro can help to assess the potential contribution of any given batch of semen and identify potential problems to the successful outcome of ICSI.