In those cases, only one type of test was used -- one that failed to detect the disease in an infected Texas cow.
The department posted the information on its Web site because of an inquiry from the Associated Press.
Conducted over the past 14 months, the tests have not been included in the department's running tally of mad cow disease tests since last summer. That total reached 439,126 at midweek.
Officials said they intended to report the undisclosed tests in an annual report later.