The Chicago Tribune reported on May 4, 2006 that the government has given up trying to track the origin of an Alabama cow infected with mad cow disease. The trail went cold after seven weeks of investigation of more than three dozen farms, the Agriculture Department said in a report issued late Tuesday. The cow was a "downer," meaning she couldn't walk, when an Alabama veterinarian examined her in late February. The vet killed the cow and removed brain samples for testing, and the cow became the nation's third case of mad cow disease. Meanwhile, in a separate case, the U.S. is tracing 15 cattle imported from Canada that ate the same feed as an infected cow discovered last month in British Columbia. So far, the government has found one cow and intends to kill and test it, the Agriculture Department said.