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Progesterone devices are broadly used in the control of reproductive management in livestock. They work by increasing circulating plasma progesterone levels with the following consequences: # Progesterone suppresses the secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus. This is done via a negative feedback to the hypothalamus neuroendocrine cells, by inhibition of KiSSpeptin KiSS1-derived peptide receptor, a protein needed for the release of GnRH. # Low levels of GnRH prevent the emergence of a dominant follicle by reducing the 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. ==Methods of progesterone administration== * 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Progesterone devices used in farm animals」の詳細全文を読む スポンサード リンク
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