Synchronization and Factors Affecting Pregnancy Rates in Embryo Transfer Recipients

摘要

Although embryo transfer technology has been used commercially for many years, the inefficiency in estrus detection, especially in bos indicus derived cattle, has limited the widespread application of this technology. The most useful alternative to increase the number of animals involved in an embryo transfer program is the use of protocols that allow for embryo transfer without the need for estrus detection, usually called fixed-time embryo transfer (FTET) protocols. Most of the currently used FTETprotocols are based on progestogen/progesterone-releasing devices combined with estradiol or GnRH, that control follicular wave dynamics and ovulation. Conception rates to a single FTET have been reported to be similar to those after detection of spontaneous estrus, but pregnancy rates have been consistently higher because these treatments have increased the number of recipients that received an embryo over those treated. Recent changes incorporated into treatments for FTET, such as the administration of eCG and the changes in the timing of PGF treatment, have resulted in increased pregnancy rates and provide opportunities to make these treatments easier to perform by farm personnel. In addition, other factors have to be taken into consideration in large scale embryo transfer programs to achieve the improved pregnancy rates.