Reproductive cloning, or the production of offspring by nuclear transfer, is often regarded as having potential for conserving endangered species of wildlife. Currently, however, low success rates for reproductive cloning limit the practical application of this technique to experimental use and proof of principle investigations. In this review, we consider how cloning may contribute to wildlife conservation strategies. The cloning of endangered mammals presents practical problems, many of which stem from the paucity of knowledge about their basic reproductive biology. However, situations may arise where resources could be targeted at recovering lost or under-represented genetic lines; these could then contribute to the future fitness of the population. Approaches of this type would be preferable to the indiscriminate generation of large numbers of identical individuals. Applying cloning technology to non-mammalian vertebrates may be more practical than attempting to use conventional reproductive technologies. As the scientific background to cloning technology was pioneered using amphibians, it may be possible to breed imminently threatened amphibians, or even restore extinct amphibian species, by the use of cloning. In this respect species with external embryonic development may have an advantage over mammals as developmental abnormalities associated with inappropriate embryonic reprogramming would not be relevant.
The objective of this study was to determine whether faecal progestagen measurement could be used to diagnose pregnancy in wild black rhinoceros cows. Immunoreactive 20alpha-progestagens were measured in faecal samples collected regularly (one or two times times per week) from pregnant and non-pregnant wild black rhinoceros females (n = 6) in Zimbabwe. Fresh dung piles deposited by the study animals were serially sampled during prolonged periods of tracking with local game scouts. Samples were stored frozen, and dried prior to methanol extraction. Immunoreactivity in faecal extracts was measured with a 20alpha-dihydroprogesterone enzyme immunoassay and was shown to reflect circulating progesterone concentrations. Mean concentrations of faecal 20alpha-progestagens during each month of gestation were significantly higher than faecal concentrations in non-pregnant animals (P<0.05), except during the second month of gestation. Faecal 20alpha-progestagens remained 5-10 times higher than concentrations in non-pregnant animals from the 4th to 15th month of gestation. It was concluded that regular non-invasive reproductive monitoring of black rhinoceros in the wild was possible and that pregnancy could be accurately diagnosed from the measurement of 20alpha-progestagens in faecal samples. The use of this technique in wild black rhinoceros populations will offer new perspectives for in situ management of this endangered species.
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