With a commodity like Jersey cattle, where demand outstrips supply, cloning may even present solutions to population problems. However, at present, cloning technology remains highly inefficient. Scientists are unsure why success rates in cloning experiments remain extremely low. The UT Cloning Project achieved Millie from an initial group of 95 embryos, which is a significant improvement over the rate of one in 277 attempts that produced Dolly in 1996. Still, the extremely high rate of fetal loss remains one of the great mysteries of cloning.
Fetal loss is also of vital importance to producers using standard breeding programs.
The UT Cloning Project used ultrasound technology to monitor the progress of nine cloned embryos and their successful implantations in surrogate heifers, and the results were extremely revealing. The data may help pinpoint exactly when and why the majority of clones are lost during early pregnancy. The findings have already narrowed the most likely date of early pregnancy loss to between 38 and 50 days of gestation. Pinpointing the exact causes for loss during specific times in a pregnancy can help us learn what measures to take to prevent losses. This would help improve the efficiency of cloning and would likely also enhance our knowledge of general bovine fertility.