Simplification of superovulation protocols in cattle
Bó, Gabriel ATríbulo, AndrésRamos, MartínGuerrero, Daniel CarballoTribulo, RicardoTribulo, HumbertoRogan, DraganMapletoft, Reuben J
Background: Successful bovine embryo transfer programs require the use of simple superovulation protocols and high numbers of transferable embryos. The control of follicular wave emergence and ovulation have facilitated donor management, but the most commonly used treatment, estradiol, cannot be used in many parts of the world, and mechanical removal of the dominant follicle is difficult to apply in the field. Other alternatives include GnRH or LH, but efficacy in groups of randomly cycling animals is variable. Review: An alternative treatment to control follicular wave emergence is to increase the response to GnRH by inducing a persistent follicle and initiating FSH treatments following GnRH-induced ovulation. The number of transferable embryos following superovulation during the first follicular wave arising at the time of the GnRH-induced ovulation did not differ from that achieved 4 days after treatment with estradiol benzoate and progesterone. To further simplify superovulation, FSH has been diluted in a slow-release formulation (SRF) and administered as a single or a split intramuscular injection. Although, a single intramuscular injection of Folltropin-V in SRF was highly efficacious in the induction of superovulation in a variety of breeds of beef cattle, it was difficult to mix with Folltropin-V. However, in a subsequent series of experiments it was shown that reducing the initial concentration of SRF to 25% and administering the Folltropin-V as two intramuscular injections 48 hours apart (called split-single administration) facilitated the dilution of Folltropin-V with the SRF and resulted in a superovulatory response that did not differ from controls. Conclusion: The incorporation of GnRH-based protocol to control follicular dynamics and ovulation have the advantage of being able to schedule the treatments quickly and without the need for detecting estrus in donor cows. The single split intramuscular injection of Folltropin-V in 25% SRF has the potential to reduce labor and handling and may be useful when handling stress is an impediment to success. These treatments are practical and easy to perform by the farm staff, facilitating the widespread application of embryo transfer technologies.
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