Scoping review of primary studies evaluating Bovine in vitro oocyte maturation and embryo development

Abstract

We conducted a scoping review to 1) map and categorize published studies reporting interventions during the in vitro production of Bovine embryos and 2) qualitatively summarize the effects of treatments based on hormones, growth factors, sera, and reproductive fluids during oocyte maturation and embryo development. We searched electronic databases using keywords ('Bovine', 'embryo', 'blastocyst', 'oocyte', 'in vitro', 'quality') derived from the PIOS approach of the PRISMA statement. We identified 231 studies published during 2000−2021, with 133 being published between 2012 and 2021. The 231 studies were classified into four treatment categories: culture conditions (28), medium composition (45), bioactive supplements (79), and other additives (79), with 19 subcategories within these categories. A total of 77 studies included hormones, growth factors, sera, and reproductive fluids, among which 53 studies reported a positive effect on embryo production. Hormone-based treatments using melatonin, gonadotropins, and steroids were the most effective, followed by interventions assessing growth factors such as EGF, FGF, IGF-1, and BMP. These treatments improved oocyte competence, cytoplasmic/nuclear maturation, oocyte quality, and blastocyst development. Although free-serum media and synthetic/alternative products can partially or totally replace serum, it is sometimes necessary even at low concentrations. At high concentrations, hormones or growth factors may have detrimental effects on oocyte nuclear maturation, impair embryo development, and decrease embryo survival. Further meta-analyses are needed to estimate the intervention-specific effects. Future research should focus on interventions that have a positive effect and can be used extensively for Bovine production.