ReBreed21-ET: Evaluation of a rapid resynchronization program that allows timed embryo transfer every 21 days

Area of Science:

• Reproductive endocrinology and artificial insemination in cattle.
• Embryo transfer technology and reproductive efficiency in livestock.

Background:

• Timed embryo transfer (TET) programs are crucial for improving reproductive efficiency in cattle breeding programs.
• Optimizing ovulation synchronization protocols is essential for maximizing pregnancy rates and minimizing the time to pregnancy.

Purpose of the Study:

• To evaluate the efficiency of a novel rapid resynchronization of ovulation program (ReBreed21-ET) for timed embryo transfer (TET) every 21 days.
• To compare the ReBreed21-ET program with a traditional resynchronization program (Resynch28) in Holstein heifers.

Main Methods:

• A total of 510 Holstein heifers were subjected to an initial ovulation synchronization protocol.
• Following the first TET, heifers were randomized into either the ReBreed21-ET (TET every 21 days) or Resynch28 (TET every 35 days) program for a 105-day period.
• Hormonal interventions including progesterone inserts, GnRH, and PGF2α, along with ultrasound pregnancy diagnoses, were used to manage the synchronization and TET cycles.

Main Results:

• The ReBreed21-ET program resulted in a higher pregnancy per ET (P/ET) for the first TET (52% vs. 39.4%) compared to Resynch28.
• Subsequent TETs showed similar P/ET between programs (approximately 40.4% vs. 40.8%).
• The ReBreed21-ET program led to an approximately 8-day earlier time to pregnancy and significantly higher overall cumulative pregnancies (75.2% vs. 64%) by the end of the 105-day season.

Conclusions:

• The ReBreed21-ET program demonstrates superior efficiency in timed embryo transfer programs by enabling more frequent embryo transfers.
• This rapid resynchronization protocol effectively reduces the time to pregnancy and increases overall pregnancy success in heifer recipients.
• The ReBreed21-ET program offers a valuable advancement for optimizing cattle breeding efficiency through improved reproductive technologies.