# Effect of Melatonin Supplementation on In Vitro Developmental Competence of Bovine Oocyte: A Systematic Review and Meta-Analysis

## TL;DR

This study reviews how adding melatonin to in vitro embryo production in cattle affects embryo development, finding it improves maturation and early development more when added during maturation rather than culture.

## Contribution

The study provides the first comprehensive meta-analysis of melatonin's effects on bovine in vitro embryo production across different stages.

## Key findings

- Melatonin in maturation media improves nuclear maturation, cleavage, and blastocyst rates in cattle embryos.
- Low melatonin concentrations are more effective than higher ones in enhancing embryo development.
- Melatonin in culture media only improves hatching rates without affecting cleavage or blastocyst formation.

## Abstract

Melatonin application in in vitro embryo production (IVEP) constitutes a promising research focus. Nevertheless, there remains a lack of comprehensive meta-analytical evidence assessing its effects in the bovine species. The present systematic review and meta-analysis study performed an in-depth overview of the effects of melatonin in different steps of the IVEP in cattle to provide insights into its application. A literature search on three major databases identified related articles until 3 December 2024. The overall effect was calculated as odds ratio (OR) and 95% confidence interval (CI) in the random effects model. Meta-analysis revealed that melatonin in maturation media significantly increased nuclear maturation rate [OR = 1.33 (1.11, 1.60), p=0.002], cleavage rate [OR = 1.26 (1.11, 1.43), p ≤ 0.001], and blastocyst rate [OR = 1.27 (1.14, 1.43), p ≤ 0.001], while it did not affect the hatching rate of blastocysts. Subgroup analysis based on the concentration of melatonin demonstrated that low concentration was superior in effects. Melatonin in culture media did not affect the odds of cleaved embryos, and blastocysts, however, increased the rate of hatching [OR = 1.35 (1.04, 1.76), p=0.025]. Subgroup analysis showed the significant effect of low and moderate concentrations on the odds of blastocysts and hatched blastocysts. No publication bias was detected. Descriptive synthesis of data suggested improvements in maturation, developmental quality, fertilization ability, and epigenetic modification during maturation and enhancement in the quality of embryos through modifications in transcription in blastocysts to alleviate apoptosis during culture. This review concludes that the application of melatonin is more promising in maturation media than in culture.