Following the introduction of bucks on day 0 to isolated does there are peaks of oestrus on day 3 and day 7. While the day 3 peak is associated with low conception rates the day 7 peak is useful for partial synchrony for artificial insemination (AI). In this trial near Te Kuiti oestrous does were drafted off twice daily, starting day 5, following buck introduction. Those drafted in the evening were artificially inseminated laparoscopically with frozen- thawed semen the next morning and those drafted in the morning were artificially inseminated in the afternoon. On two farms the proportion of 207 and 123 mature does artificially inseminated on day 7-8 (day0=April 11) were 55% and 74% respectively, on day 6-10 inclusive 87% and 94% were artificially inseminated. On farm 1 on day 7-8 and day 6- 10 only 25% and 28% of 205 two tooths were artificially inseminated, in contrast on farm 2 74% and 84% of 70 two tooths were artificially inseminated. The farm 1 two tooths were 3.6 kg lighter than those on farm 2. CIDR-PMSG synchronised does from farm 1 (48 mature and 33 two tooth) were AIed on-time on days 6 and 10. There was no significant difference between the pregnancy rates of the CIDR synchronised (60%) and the buck induced does (56%). There were additive effects of type of oestrus induction and live weight on the % multiple pregnant. At 20 kg live weight the predictions of the % multiple pregnant were buck effect 11%, CIDR-PMSG 26%, and at 30 kg live weight 51% and 75% respectively.

CA, Morris, and VR Carruthers

Proceedings of the New Zealand Society of Animal Production, Volume 51, , 103-106, 1991
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