Besides the fact that they are are larger species of animals then a deer. They are also domestic and are located in an area with one of the most nutrient dense soils. I am tracking down some research that has the breakdown of key ingredients based of cervide used for velveting.
Another major reason we use Elk is because they have the lowest recored cases of Chronic Wasting Disease, CWD, ( less 1% of the population), even less then New Zealand Velvet. Contrary to popular belief there has been recorded cases of CWD in New Zealand and the farms that harvest antler also slaughter the animals on the same grounds. Our farms are located in Northern Idaho, are slaughter free and there has never been a case of CWD in Idaho. Further more, the CDC has never recorded a case of CWD or prion* transmission to humans. To be safe, we test for IGF-1 content, prions and other forms of bacteria among other things. The 190 proof alcohol also plays a very vital role in destroying any forms of bacteria that may be in the harvested raw material.
*Prion - A prion is a small infectious particle composed of abnormally folded protein that causes progressive neurodegenerative conditions.