Expression of estrus as a relevant factor in fixed-time embryo transfer programs using estradiol/progesterone-based...

Area of Science:

• Animal Science
• Reproductive Biology
• Beef Cattle Production

Background:

• Embryo transfer (ET) accelerates genetic progress in beef herds.
• Estrus synchronization and fixed-time embryo transfer (FTET) have improved recipient utilization.
• Factors like nutrition and management influence ET success.

Purpose of the Study:

• To review the impact of estrus expression and estradiol on bovine embryo development and pregnancy outcomes.
• To evaluate the effectiveness of current fixed-time embryo transfer protocols.
• To highlight the importance of estrus expression in recipient cattle for successful embryo transfer.

Main Methods:

• Review of research on estrus synchronization and fixed-time embryo transfer protocols.
• Analysis of studies investigating the role of estrus expression and estradiol in preovulatory follicle development.
• Examination of pregnancy rates and losses in recipients of frozen/thawed bovine embryos.

Main Results:

• Estrus expression is positively correlated with higher pregnancy rates in recipient cattle.
• Increased estrus expression is associated with reduced pregnancy losses after embryo transfer.
• Fixed-time embryo transfer protocols, while effective, may not fully account for the benefits of natural estrus expression.

Conclusions:

• Estrus expression is a critical factor for optimizing pregnancy success in bovine embryo transfer.
• Future research should focus on protocols that enhance or incorporate natural estrus expression for improved outcomes.
• Integrating estrus expression considerations into fixed-time embryo transfer protocols can further accelerate genetic gain in beef operations.