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:

1. Progesterone suppresses the release of GnRH.
2. 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.
3. A dominant follicle develops but there is no ovulation as LH release is prevented by suppression of GnRH.
4. Removal of progesterone device produces a surge of GnRH, generating a pulse of LH that induces ovulation.

Clinical uses of PRID

^[1]

1. 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.

1. Induction of oestrus in anoestrus cows^[4]
2. Treatment of follicular cysts
3. Persistent ovarian follicles
4. Improve oocyte quality
5. Reduction of early embryonic death and improved fertility
6. Treatment of repeat breeders
7. Increased fertility in embryo transfer protocols

References

1. Reproduction in Cattle. A.R. Peters and P.J.H. Ball
2. Deletang et al. (2006). Efficacy of PRID with injection of PGF2a for synchronising oestrus in French dairy and beef cattle. World Biuatric Congress.
3. 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
4. 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