This study reports on the performance of some of the original animals used to establish the Invermay deer farm. These comprised a selection of some of the original 1973 animals, 21 hinds of unknown age and 19 of the first hind calves born at Invermay in that year. Reproductive performance, expressed as the percentage of hinds weaning calves, decreased slowly from 90% at 6 and 7 years of age, to 50% at 17 years, then dropped markedly with only one calf being successfully reared in each season when the hinds were 19 and 20 years. Similarly, few (5/21) of the older unknown-age hinds raised calves when > 17 years old. When blood sampled twice-weekly during the breeding season (rising 21 years of age), only 6/12 of the known-age hinds had significant plasma progesterone concentrations, with only 3 animals displaying anything like normal cyclical patterns. In addition, most had elevated plasma LH concentrations. Post mortem examination revealed that all these hinds had small reproductive tracts and very few ovarian follicles at this age. Despite an ability to live beyond 20 years, these results suggest that waning reproductive performance with age may be due to ovarian failure.
Proceedings of the New Zealand Society of Animal Production, Volume 56, , 344-346, 1996
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