CIDR - A NEW PROGESTERONE-RELEASING INTRAVAGINAL DEVICE FOR INDUCTIONOF ESTRUS AND CYCLE CONTROL IN SHEEP AND GOATS

The controlled internal drug release dispenser (CIDR) is an intravagin al device constructed of a progesterone-impregnated medical silicone e lastomer molded over a nylon core. The CIDR-G is suitable for treatmen t 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 th e breeding season, CIDR were used to synchronize estrus. The bulk of e wes 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 go nadotropin (PMSG). Both types of pessaries were effective when used wi th PMSG. Percentages of ewes bred, ewes lambing and lambs born were si milar for sponge and CIDR-treated ewes. Out-of-season breeding also wa s stimulated without PMSG. For this purpose, CIDR were applied in conj unction with the ram effect. A month before the onset of the normal br eeding period, ewes were treated with CIDR and then exposed to rams. E strus, conception and lambing were advanced in ewes that had received CIDR compared with those that had not. In a subsequent experiment, bre eding was advanced, and after lambing and lactation, ewes were retreat ed with CIDR/ram effect in late winter/early spring. Most ewes (94%) l ambed the following summer. In goats, CIDR have been substituted succe ssfully for sponges for estrous synchronization, superovulation, artif icial insemination and embryo transfer. The CIDR-G provides a convenie nt means to deliver exogenous progesterone to sheep and goats and offe rs an alternative to the progestogen sponge for reproductive managemen t.