Synchronization of oestrus in sheep: The use of controlled internal drug release (CIDR) dispensers

The use of the CIDR (controlled internal drug release) dispenser as a progestagen-synchronizing agent was evaluated in 37 Karakul ewes during the breeding season, using the intravaginal progestagen sponge as a control (30 ewes). Although there was no significant differences in oestrous response, following intravaginal insertion for 14days, between these two progestagen devices, the time from device withdrawal to the onset of the induced oestrous period (31,2 vs 62,5 h) and the duration of the induced oestrous period (32,7 vs 47,4 h) was significantly (P<0,01) shorter in the CIDR dispenser group. The mean time from device withdrawal to the serum preovulatory LH peak and the interval from the onset of oestrus to the pre-ovulatory LH peak was significantly (P<O,Ol) earlier in the CIDR dispenser group (28,0 vs 78,0 hand 5,3 vs 17,3 h respectively). No significant difference in the serum progesterone concentrations was noted between the two groups. No significant difference in reproductive performance was obtained with conception, lambing rates and fecundities of 72,2 vs 79,3%; 75,0 vs 89% and 103,8 vs 113,0% for the dispenser and sponge treatment groups respectively. Results confirm the potential of the CIDR dispenser as an efficient synchronizing agent and the more concentrated synchrony obtained makes it ideal for fixed-time insemination.