From the Fort Collins Coloradoan (Jacy Marmaduke):

“This is kind of our mini-Yellowstone, so to speak,” said Mark Sears, standing before a crowd of 500 and gesturing toward the corral just minutes before the release about 2:45 p.m. Sunday.

Sears, Fort Collins’ natural areas program manager, was referring to the herd’s genetic origins in the Yellowstone National Park plains bison herd, which numbers more than 3,500 and is easily the largest in the world.

But bringing a bit of Yellowstone to Northern Colorado was easier said than done: Brucellosis, a contagious disease that causes cattle to abort, is ubiquitous among the Wyoming herd and has tempered the resurgence of genetically pure bison. Today, most of the 500,000 remaining bison in the U.S. and Canada have at least some domestic cow DNA because of interbreeding.

So Colorado State University researchers worked with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service to scrub Yellowstone semen and embryos of brucellosis, creating genetically pure, disease-free bison.