In vitro embryo production (IVP) is now the predominant technique utilized to generate embryos for transfer in cattle. Although artificial insemination and natural mating remain the main breeding methods, the number of embryos produced through IVP exceeds those derived in vivo (IVD). Superstimulation with follicle-stimulating hormone (FSH) is necessary for IVD embryos and is frequently used in IVP to increase follicular development. However, despite the industry shift from IVD to IVP, the success of IVP embryos remains poor. This study systematically evaluated embryo production outcomes from in vivo and in vitro systems in Bos taurus beef and dairy cattle, with a focus on FSH superstimulation. Data from published studies were integrated to compare oocyte yield, embryo production, and developmental rates. Overall, OPU yields more oocytes in both beef and dairy cattle relative to recovered structures by uterine flush, but this did not consistently translate into higher embryo numbers. Importantly, embryo outcomes differed by both cattle purpose (beef/dairy) and whether embryo counts or rates were considered. Beef cattle produced more transferable embryos (counts) under IVD than IVP, whereas dairy cattle had comparable embryo counts between techniques. In contrast, embryo rates (percentage of embryos relative to oocytes/structures recovered) were similar between IVD and IVP in both beef and dairy. These findings demonstrate that embryo production outcomes depend on whether absolute counts or proportional success rates are evaluated. While FSH improves follicular response, it does not consistently increase embryo yield. Further refinement of reproductive strategies is needed to optimize embryo production efficiency across systems.
Castro et al. (2026) studied this question.