Eighty mature fallow deer does were allocated to four treatment groups (n+20) for which oestrous synchronization treatment consisted of intravaginal insertion of single CIDR devices for 14 days and prostaglandin administration on days 0 and 10 of device insertion. Treatment groups were staggered successively by 7-day intervals from early March to late May, the period spanning the natural mating season (rut). Observations to determine the onset of oestrus were performed 24-72 hours after CIDR device withdrawal and blood samples were collected four times during insertion and then every 2 days, for 14 days, from CIDR device withdrawal. Plasma samples were analysed for progesterone concentration to determine luteal development. A group of untreated contemporary control does were allowed to mate naturally to crayon-harnessed bucks to determine the period of the 1990 natural rut. Oestrus and ovulation were detected on 69% and 80% of occasions respectively following CIDR device withdrawal, with ovulation following oestrus on 98% of occasions. Ovulation not preceded by observed oestrus, probably representing silent ovulations, occurred early in the breeding season. There was complete failure of response, in terms of does exhibiting oestrus increased from 0-10% to 89-100% with the greatest coinciding with the onset of the natural rut. In addition, the mean interval from CIDR device withdrawal to onset of oestrus tended to decrease from between 71-88h to 47-63h and oestrous synchrony improved progressively during the trial. The efficacy of CIDR devices in synchronizing oestrus and ovulation in fallow deer does is clearly influenced by timing of treatment relative to the natural breeding season of the herd.
Proceedings of the New Zealand Society of Animal Production, Volume 52, , 125-128, 1992
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