From mouse embryo assay to bovine embryo assay: towards an ethical and scientifically superior quality control standard in assisted reproduction technologies

Abstract

The mouse embryo assay (MEA) is the standard test used in assisted reproduction to evaluate the toxicity and effectiveness of culture media and consumables. However, the assay has been criticised for its limited sensitivity, inconsistencies between laboratories, and ethical concerns. Despite the 3Rs principles, over 111 million mice and rats were used in the USA in 2017, with an unknown proportion of these being used in the MEA. While the FDA has provided MEA guidelines, its aim is to phase out animal toxicity testing within 3-5 years. This article explores the possibility of replacing the MEA with the bovine embryo assay (BEA), providing justifications based on ethics, science, practicality, and economics. Through a review of MEA applications, market data, regulatory frameworks and industry disclosures, the article estimates the current impact of the MEA. Incorporating the BEA into regulations could eliminate the need to breed mice for the MEA and greatly reduce the use of animals. Standardising and validating the BEA would provide a reliable and ethically preferable alternative that aligns with the growing demand from regulators and society for non-animal testing methods.