"They started flopping over and dying.” A Colorado rancher from XO Cattle Company is grappling with the mysterious deaths of 16 cattle, most of them heifers that had recently calved or were about to. The incident began on May 8, when three cattle were found dead, followed by a dozen more collapsing later that day. Despite investigations by veterinarians, state officials, and environmental agencies, no definitive cause has been identified. The unexplained losses are estimated at $5,000 per head.

A large herd of cattle was driven through a town in Colorado on Thursday to reach their summer grazing grounds. | CBS News