Timing of the LH peak and ovulations in superovulated Coopworth ewes synchronised with progesterone-containing CIDRĆ device inserted for 12d [1-CIDR] vs. one device inserted for 9d, then replaced with a second device for 3d [2-CIDR] on the time to the onset of oestrus (OO) and the pre-ovulatory LH peak (PLH) from device withdrawal. In Experiment 2, 78 ewes were treated with the 2-CIDR regime and 800iu PMSG + 12mg FSH. Ewes were allocated to 6 groups (n+12) and ovaries were examined by laparoscopy at 34, 38, 42, 46, 50 or 54 h following device withdrawal. Pre-ovulatory follicles and ovulations were recorded. Plasma samples were taken from a further group (n=6) to determine time to the LH peak. In Experiment 1, ovulation rates (OR) were 1.6 ą 2, 9.0 ą 2.2 and 8.3 ą 1.5 and 1.7 ą .3, 10.5 ą 2.5, 11.2 ą 1.5, for ewes treated with 0, 800 ą 12 and 800 ą 18 for 1-CIDR or 2-CIDR, respectively. Overall, there was a significant increase in time to OO (P<.05) and PLH (P<,001) between 1- CIDR and 2-CIDR ewes, but no effect on either OR or total stimulations (TS). Gonadotrophin treatment increased OR, TS, OO and PLH (P<.001, respectively). However, except for OO, no difference was observed between 800 + 12 and 800 + 18 ewes. In Experiment 2, no significant difference was observed for TS between the 6 groups (mean ą SE = 6.6 ą 0.4). However, ovulation rate significantly increased over time (P<.001). Fitting a quadratic function revealed that by 45 h post-CIDRĆ withdrawal, 75% of follicles were predicted to have ovulated. Time to LH peak in sampled ewes was 22 ą 1 h from device withdrawal, which was similar to that observed in Experiment 1 (20 ą 1 h). Keywords: NZSAPAB; Superovulation; CIDR device; LH; ovulations; sheep.
Download abstract in text format
Last Updated 25-01-1997