Exogenous Melatonin Directly and Indirectly Influences Sheep Oocytes

Area of Science:

• Reproductive Biology
• Animal Science
• Endocrinology

Background:

• Melatonin (MT) influences estrus regulation in sheep, crucial for seasonal breeding.
• Conflicting results exist regarding MT's effect on sheep oocyte developmental competence.
• Understanding MT's impact is vital for predicting sheep oocyte response to estrus manipulation.

Purpose of the Study:

• To conduct a meta-analysis on the direct and indirect effects of melatonin on sheep oocytes.
• To evaluate melatonin's influence on in vitro and in vivo sheep oocyte development and reproductive parameters.

Main Methods:

• Meta-analysis of 433 collected articles, with 20 articles and 34 treatments selected.
• Estimation method established for litter size analysis.
• Analysis of in vitro maturation medium and subcutaneous implantation effects on oocyte parameters.

Main Results:

• Exogenous MT in vitro maturation medium positively correlated with blastocyst rates.
• Subcutaneous MT implants did not affect in vivo ovulation, fertilization, blastocyst, or pregnancy rates.
• MT did not affect in vitro cleavage rates but improved in vivo cleavage rates.

Conclusions:

• In vitro melatonin enhances sheep oocyte blastocyst rates.
• In vivo melatonin implants do not improve key reproductive outcomes but do improve cleavage rates.
• Further research into pyroptosis and animal welfare implications of MT implantation is recommended.