The U.S. Food and Drug Administration (FDA) this summer approved the EAZI-BREED CIDR cattle insert for synchronizing estrus in dairy heifers and beef cattle. It is not approved for lactating dairy cows; however, submission to the FDA for its use in lactating cows has occurred and is now being reviewed. CIDR is the common name and this acronym stands for controlled internal drug-releasing device. Approximately 15 years of research around the world has been conducted on this device and the concept of supplying progesterone in a slow constant release over a period of several days. During my research study leave to New Zealand in 1994 I conducted studies evaluating microencapsulated semen using heifers and lactating cows that were synchronized to allow a timed insemination following CIDR removal. A similar CIDR device has been used in both Mexico and Canada for a number of years and by many U.S. embryo transfer veterinarians for synchronizing embryo recipients. The CIDR device has a T-shaped hard nylon body with a silicone cover which is saturated with progesterone. The progesterone in the CIDR is the natural progesterone secreted by the corpus luteum (CL) 5 days after ovulation and for the entire duration of pregnancy. Progesterone is the hormone required to maintain pregnancy and in cycling non-pregnant females it prevents ovulation and the expression of estrus. To insert the CIDR device into its applicator the two wings must be pushed together. It is important to clean the vulva prior to insertion of the device. At withdrawal 7-days following insertion simply give the plastic string or tail a gentle pull to remove it from the vagina. If more than 5% of the heifers lose the device the tail should be clipped so only 2 to 3 inches protrude from the vulva. The CIDR device approved in the U.S. contains less total progesterone than the device sold in Mexico and Canada, but the daily release of progesterone from the two CIDR devices is similar. The CIDR was approved as a single service device because it can not be cleaned or disinfected sufficiently to allow safe reuse without the chance of introducing organisms into the reproductive tract. The CIDR device is inserted for 7 days and a luteolytic dose of prostaglandin (5 ml of Lutalyse or 2 ml of Estrumate) is administered on day six or the day before CIDR removal. If the CL is viable at the time of Lutalyse administration on Day 6, the CL will regress and heat occurs usually 36 to 48 hours after CIDR removal. If the heifer was not cycling or the CL regressed prior to Lutalyse administration on Day 6, progesterone from the CIDR prevents heat until about 24 to 36 hours after removal on Day 7. The CIDR-7 with Lutalyse on Day 6 provides good synchrony of estrus and pregnancy rates. A major advantage of the CIDR system is that it will induce estrus in a higher percentage of anestrous (non-cycling) cows and prepubertal heifers.

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