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Progesterone Releasing Intravaginal Device (PRID). For use in cattle and buffalo. They consist on a stainless spiral coil coated with an inert silicone rubber matrix impregnated in progesterone (1.55g). It has a nylon string that is placed hanging out of the vagina. Tying a loop on the string can facilitate removal of the device in the event the string is shortened to prevent rogue heifers or cows pulling them out. The coil has been in the market for over 30 years now, originally including a capsule of oestradiol valerate. The use of oestrogens in the food producing industry in the EU was banned in 1981 because of their suggested carcinogenic effects. These substances are still approved for use in the US and many other countries, including Australia, Canada and New Zealand. The coil is licensed to use with fixed time artificial insemination
Controlled Internal Drug Release (CIDR). For use in cattle and buffalo. This is a T-shaped silicone elastomer device impregnated in progesterone (1.38g). It has a plastic tail to ease removal.
The curve of plasma progesterone in ovariectomised cows fitted with either PRID or CIDR show similar overall levels with a more obvious initial peak in the coil versus the t-shaped device. It has been suggested that this increased level of plasma progesterone is due to optimal contact of the coil with the vaginal walls. Some heifers resent insertion of either device as it involves penetration of the hymen.
Device retention is high (around 98%) in both PRID and CIRD. Reasons for loss include overlubrication, pneumovagina, rogue cows pulling out the nylon string or plastic tail and slack cows, large breeds after several calvings.
Synchronisation of oestrus in conjunction with prostaglandin F2α. 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: Progesterone 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.