Here is some info.
Cytoplasmic hybrids, or cybrids, can be made by placing the nucleus from a human cell into an animal egg that has had its nucleus removed. The genetic material in the resulting embryos is 99.9 per cent human. This could help to replace a dwindling stem cell population.

Also, here is a link to more info on the topic.
http://www.scientistsolutions.com/t6463-Cow_human+hybrid+eggs+%22cowboys%22.html

Its up for a vote in the Senate. What do scientists think?