USDA tested a total of 67 cows from the herd of an animal infected with bovine spongiform encephalopathy over the past several days.
Investigators have been working to identify offspring and herd mates born within a year of the infected cow's birth. The infected cow was a 12-year-old Brahma cross beef cow.
Testing was conducted on two groups removed from the herd at a Texas ranch. The infected animal spent its entire life on the Texas ranch. The National Veterinary Services Laboratory in Ames, Iowa, tested 29 cows on Wednesday and 38 on Friday.