Twenty-nine cows tested negative for mad cow disease after they were culled from the same herd where an infected cow had been found, the Agriculture Department said yesterday. Tests of 38 more cows from the herd are pending, officials said.
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.
The 29 adult cows were removed from the herd on Wednesday and killed, and tissue samples were collected for testing, the department said.
The department said yesterday that those 29 adult cows tested negative, according to the National Veterinary Services Laboratory in Ames, Iowa. Samples from an additional 38 cows received Friday are pending, the department said. In all, 67 animals were removed from the herd for testing.
The infected cow spent its entire life on the same farm, which the government has not identified. It was sold through a livestock market on Nov. 11 but was dead on arrival four days later at a slaughterhouse, the department said. It was then taken to a pet food plant in Waco, Tex., which did not use it for food but removed brain tissue for testing.
Screening called a "rapid test" indicated the presence of mad cow disease in the animal, but results from another test were negative. The government announced that the animal was free of the brain-wasting disease. Last month, the agency's internal watchdog ordered a third type of test that came back positive. A lab in England confirmed the results June 24.