Progesterone releasing devices are used to induce and synchronise oestrus in ewes and to provide supplementary progesterone post-mating to increase embryo survival. Because of its physical characteristics the Type-G CIDR device can be washed and re-used. Two trials each involving 1200 ewes were conducted. CIDR devices previously used for 14 days were evaluated in comparison to unused devices for their efficacy in; (1) induction and synchronisation of oestrus (50 ewes were treated with either new or used devices each month of the year with 400 I.U. PMSG given at device removal and the onset of oestrus and pregnancy monitored) or (ii) treatment post-mating (new, used or no devices were reinstated into groups of 33 ewes on Day 6 after a synchronised mating each month of the year. Pregnancy and lambing rates were monitored). Fewer ewes exhibited oestrus after treatment with the used CIDR devices and fewer became pregnant in Trial 1. There was no effect of post-mating treatment on pregnancy rate in Trial 2 but such treatment reduced the proportion of ewes have multiple births. Monthly variations in response were seen in both trials.
Proceedings of the New Zealand Society of Animal Production, Volume 51, , 79-84, 1991
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