CIDR: A new progesterone-releasing intravaginal device for induction of estrus and cycle control in sheep and goats

The controlled internal drug release dispenser (CIDR) is an intravaginal device constructed of a progesterone-impregnated medical silicone elastomer molded over a nylon core. The CIDR-G is suitable for treatment of parous ewes, lambs and goats. Plasma progesterone levels increase rapidly after insertion of CIDR, reach highest concentrations on Day 3 and then gradually decrease. In an on-farm trial conducted during the breeding season, CIDR were used to synchronize estrus. The bulk of ewes lambed within 6 days of each other. A second group of ewes lambed 16 days after the first in which 20% of ewes lambed. Sponges and CIDR were compared for out-of-season breeding using pregnant mares serum gonadotropin (PMSG). Both types of pessaries were effective when used with PMSG. Percentages of ewes bred, ewes lambing and lambs born were similar for sponge and CIDR-treated ewes. Out-of-season breeding also was stimulated without PMSG. For this purpose, CIDR were applied in conjunction with the ram effect. A month before the onset of the normal breeding period, ewes were treated with CIDR and then exposed to rams. Estrus, conception and lambing were advanced in ewes that had received CIDR compared with those that had not. In a subsequent experiment, breeding was advanced, and after lambing and lactation, ewes were retreated with CIDR/ram effect in late winter/early spring. Most ewes (94%) lambed the following summer. In goats, CIDR have been substituted successfully for sponges for estrous synchronization, superovulation, artificial insemination and embryo transfer. The CIDR-G provides a convenient means to deliver exogenous progesterone to sheep and goats and offers an alternative to the progestogen sponge for reproductive management.