[Methods for synchronizing estrus and selecting recipient heifers in embryo transplantation]

Area of Science:

• Reproductive biology
• Veterinary gynecology
• Embryo transfer technology

Background:

• Estrus synchronization is crucial for efficient artificial insemination and embryo transfer in cattle.
• Hormonal protocols aim to control the estrous cycle for improved reproductive outcomes.
• Embryo viability and recipient-embryo interactions are critical factors in successful pregnancy establishment.

Purpose of the Study:

• To compare the efficacy of two estrus synchronization protocols in heifers.
• To evaluate the success rate of embryo transplantation in synchronized heifers.
• To investigate factors affecting embryo survival and pregnancy establishment.

Main Methods:

• Estrus synchronization in 35 heifers using norgestomet implants and PMSG.
• Estrus synchronization in 73 heifers using prostaglandin F2-alfa.
• Embryo transplantation into synchronized recipient heifers.
• Monitoring conception rates, embryo survival, and pregnancy outcomes.

Main Results:

• Norgestomet implants and PMSG resulted in a 31% higher conception rate compared to prostaglandin F2-alfa.
• Embryo transplantation showed a high mortality rate of 61.8% for transplanted embryos.
• Embryo death occurred throughout gestation, and 17.10% exhibited migration to the contralateral uterine horn.

Conclusions:

• Norgestomet and PMSG offer a more effective estrus synchronization method for heifers.
• Embryo transplantation success is significantly limited by high mortality and migration rates.
• Further research is needed to improve embryo survival and reduce migration in recipient heifers.