Abstract:
The present costs and efficiencies of producing cloned embryos, pregnanciesand offspring using the simplified nuclear transfer techniques developed inthe authors’ laboratories are compared with those required for thelarge-scale application of such cloning technologies in cattle. The currentcosts in the laboratory of producing large numbers of genetically identicalcloned embryos for transfer is around $15.00 per blastocyst, which iswithin the cost estimated to be commercially viable for cloned female dairyembryos for transfer. However, the pregnancy and calving rates from thetransfer of such embryos are still well below that required for large-scalecommercial application for which ongoing pregnancy rates of at least50% per recipient will be required. The current pregnancy rate(30-40 days post-transfer) following the transfer of an average of threecloned embryos per recipient is 37%, and the calving rate 17%,representing high losses between pregnancy diagnosis and term. In the beefindustry and in some dairy situations the final product (cloned bulls fornatural mating) will have a much higher inherent value and differentparameters will therefore apply. Recent developments in the technologies thatare likely to increase the probabilities of large-scale application arediscussed, including recycling nuclear transfer embryos, somatic cell cloning,new cryopreservation techniques and automated oocyte harvesting.