Strategies to increment in vivo and in vitro embryo production and transfer in cattle

Abstract

Knowledge of follicular wave dynamics obtained through the use of real-time ultrasonography and the development of the means by which follicular wave dynamics can be controlled have provided practical approaches for the in vivo and in vitro production and transfer of embryos in cattle. The elective control of follicular wave emergence and ovulation has had a great impact on the application of on-farm embryo transfer, especially when large groups of donors need to be superstimulated at the same time. Although estradiol and progestins have been used for many years, practitioners in countries where estradiol cannot be used have turned to alternative treatments, such as mechanical follicle ablation or the administration of GnRH for the synchronization of follicle wave emergence. In vitro embryo production also benefits from the synchronization of follicle wave emergence prior to Cumulus Oocyte Complexes (COCs) recovery. As Bos indicus cattle have high antral follicle population, large numbers of oocytes can be obtained by ovum pickup (OPU) without superstimulation. However, synchronization of follicular wave emergence and superstimulation is necessary to obtain high numbers of COCs by OPU and blastocysts following in vitro fertilization in Bos taurus donors. Finally, embryos can now be transferred in commercial beef or dairy herds using efficacious synchronization and resynchronization protocols that are easily implemented by farm personnel. These technologies can also be used to resolve reproductive problems such as the reduced fertility observed during summer heat stress and/or in repeat-breeder cows in commercial dairy herds.

Synchronization with estradiol benzoate in the presence of the corpus luteum in Wagyu cows increases the number of medium follicles but does not interfere with in vitro production of embryos

“…In this context, we emphasize that the findings of the present study partially agree with data from the literature. For example, the synchronization of the follicular wave emergence before OPU had increased the number of oocytes obtained and blastocysts produced in Bos taurus, but not in Bos indicus breeds (Bó, Cedeño, & Mapletoft, 2019). Curiously, we did not find any effect of synchronization on embryo production in Bos taurus animals, whereas in Bos indicus cattle, Cavalieri et al (2018) observed that synchronization pre-OPU improved IVEP performance.…”

GnRH or estradiol benzoate combination with CIDR improves in-vivo embryo production in bovines (Bos indicus and Bos taurus) under subtropics

“…The two most important factors affecting the variability in superovulation results are the stage of the estrous cycle (follicular status of ovaries) and antral follicular count in donor cows ( Bó, Cedeño & Mapletoft, 2019 ). Based on the findings of this study and perusal of the literature, it can be inferred that treating donor cows (for synchronization of follicular wave emergence) before initiating FSH administration remains beneficial in enhancing in vivo TEs production.…”

Understanding the trade-off between the environment and fertility in cows and ewes

“…Also, high environmental temperatures (>25 0 C, either within housing, or outside without shade) reduce fertility, and this is even more dramatic for high yielding cows that also generate more heat than they can dissipate (Al Katanani et al, 1999). A useful management tool to maintain high pregnancy rates throughout the year would be to produce bovine embryos during the cooler months and use them in embryo transfer during periods of heat stress (Bo et al, 2019). Thus, providing more expensive environments or engaging intricate technologies (e.g., embryo production/transfer) are used in trade-offs against the deleterious effects of the environment on fertility (review: Dobson et al, 2001;review: Butler, 2003;Canu et al, 2010).…”