Does synchronising follicular wave emergence improve outcomes in non‐superstimulated donor cattle undergoing ovum pick‐up ( <scp>OPU</scp> ) for <i>in vitro</i> embryo production?

In vitro embryo production (IVEP) is now a widely commercialised assisted reproductive technology used in cattle reproduction. The use of follicle-stimulating hormone (FSH) to superstimulate donor cattle prior to ovum pick-up (OPU) is generally regarded as an effective strategy to improve oocyte quality, developmental competence and increase embryo development rates. However, its use is expensive, labour-intensive and subject to supply shortages and may attract negative societal perceptions of hormonal stimulation. An alternative strategy involves manipulating normal ovarian physiology through synchronising follicular wave emergence (FWE), thereby generating a homogeneous cohort of common growth phase follicles for oocyte recovery at OPU without the need for FSH. This multi-PICO critically appraised topic (CAT) examined the effectiveness of synchronising FWE as an alternative to FSH-dependent programmes in cattle IVEP. A total of 345 studies were identified, nine of which met the inclusion criteria for this study. Only two studies investigated non-oestrogen synchronisation methods, whereas seven investigated oestrogen-based protocols. The findings from the seven suitable experimental studies suggest there is currently equivocal evidence for the use of oestrogen-based synchronisation protocols prior to OPU. The Jadad grading scale adopted for appraisal found the included studies to be insufficient in providing overall certainty in results. Further research into alternative techniques, as well as alterations in study design and population sizes included, would be beneficial, as due to a lack of available evidence, no clear conclusions can be drawn.