Pregnancy loss in cattle with emphasis on embryo transfer programs.

Area of Science:

• Animal Science
• Reproductive Biology
• Veterinary Medicine

Background:

• Pregnancy loss (PL) significantly affects cattle herd reproductive efficiency and economic viability.
• In vitro embryo production (IVP) systems face challenges with PL, impacting technique success.
• Pregnancy establishment is influenced by fertilization, maternal environment, and embryonic signaling.

Purpose of the Study:

• To review factors influencing pregnancy loss in cattle, especially within IVP and embryo transfer (ET) contexts.
• To identify management strategies that can improve fertility and reduce pregnancy loss in embryo recipients.

Main Methods:

• Review of existing data on dairy and beef cattle undergoing IVP and ET.
• Analysis of factors including recipient status (cow vs. heifer), semen type, synchronization protocols, and recipient breed.
• Evaluation of the impact of estrus expression and embryo quality on pregnancy outcomes.

Main Results:

• Dairy cattle ET may show higher initial pregnancy but also greater PL than artificial insemination (AI).
• Beef cattle recipient cows had higher pregnancy per ET (P/ET) and lower PL than heifers.
• Recipient factors like breed, synchronization, estrus expression, and embryo quality significantly affect P/ET and PL.

Conclusions:

• Management strategies are crucial for improving fertility and reducing pregnancy loss in cattle embryo recipients.
• Optimizing recipient conditions and embryo selection can enhance the success of IVP and ET programs.
• Addressing factors like heat stress and recipient management can mitigate pregnancy loss in cattle.