Anergy to tuberculin in beef cattle.

Various aspects associated with anergy to tuberculin were investigated in a total of 75 tuberculous cattle. Forty-six (59%) had single lesions and 32 (41%) had multiple lesions. Forty-three (55.1%) had lesions in the lungs or associated lymph nodes and 23 (29.5%) showed multiple involvement of these tissues. Nine anergic cattle had generalised tuberculosis. Histological examination of lesions from 38 animals showed that the majority were of the progressive type. When bovine PPD tuberculin was used more cattle were anergic to the 0.1 mg than to the 0.2 mg dose and fewer tuberculous cattle were detected with either dose if tests were read at 96 h rather than 72h. Other factors thought to contribute to anergy are discussed with special reference to its relative importance in cattle with pulmonary infection.