Progesterone-releasing intravaginal device
Intravaginal progesterone devices are broadly used in the control of reproductive management in cattle. The chain-mechanism of action is as follows:
- Progesterone suppresses the release of GnRH.
- Low levels of GnRH prevent the emergence of a dominant follicle by diminishing release of LH and FSH hormones. Current follicular waves cease and a new wave emerges 3–5 days after implant.
- A dominant follicle develops but there is no ovulation as LH release is prevented by suppression of GnRH.
- Removal of progesterone device produces a surge of GnRH, generating a pulse of LH that induces ovulation.
Clinical uses of PRID
- Synchronisation of oestrus in conjunction with prostaglandin[2][3] The PGF2α injection helps to ensure there is no residual CL and the potentially ovulating follicle has been held primed for less time, enhancing its viability.
Protocol – PRID for 9 days. PGF2α injection on days 5–8. Serve on observed oestrus or fixed time once at 56h or twice at 48h and 72h.
- Induction of oestrus in anoestrus cows[4]
- Treatment of follicular cysts
- Persistent ovarian follicles
- Improve oocyte quality
- Reduction of early embryonic death and improved fertility
- Treatment of repeat breeders
- Increased fertility in embryo transfer protocols
References
- ^ Reproduction in Cattle. A.R. Peters and P.J.H. Ball
- ^ Deletang et al. (2006). Efficacy of PRID with injection of PGF2a for synchronising oestrus in French dairy and beef cattle. World Biuatric Congress.
- ^ McPhee et al. (1983). Multiple use of progesterone releasing intravaginal devices for synchronisation of oestrus and ovulation in cattle. Australian Vet Journal, 60 pp. 40–43
- ^ Tjondronegoro et al. (1987). Effects of progesterone intravaginal devices on synchronisation of oestrus in post-partum dairy cows. Journal of Dairy Sciences,70, pp. 2162–67