The efficacy of trans-anethole supplementation during in vitro culture of follicles, oocytes and embryos: A meta-analysis approach.

This study aimed to evaluate the effects of trans-anethole supplementation on in vitro reproductive outcomes using a meta-analysis approach. A total of 128 records were retrieved from four major scientific databases. After screening and eligibility assessment, 6 studies were included in the final analysis. These studies reported outcomes from in vitro follicle culture, oocyte in vitro maturation, and embryo culture across multiple species and varying concentrations of trans-anethole. Relative risks (RR) and 95 % confidence intervals (CI) were calculated, and forest plots were used for visual synthesis. Risk of bias was assessed using SYRCLE's tool. The results demonstrated a dose-dependent and species-specific effect of trans-anethole. Moderate concentrations (30-300 μg/mL) improved oocyte maturation (MII), cleavage, and blastocyst rates-particularly in goats, where MII rates increased by up to 25.8 %. In cattle, outcomes were inconsistent, with some studies reporting benefits and others showing negative effects at high doses (≥2000 μg/mL). Cleavage and embryo development followed a similar dose-response pattern. Low concentrations generally improved cleavage and blastocyst rates, while higher concentrations reduced performance, especially in goats. Significant heterogeneity (I = 73.7-100 %) was observed across studies, highlighting the influence of species, treatment stage, and concentration. Overall, trans-anethole shows promise as a supplement in ART systems, particularly at low to moderate concentrations. However, its efficacy is highly context-dependent. Further research with standardized protocols is needed to define optimal dosing strategies and clarify its mechanisms of action in reproductive biotechnology.