Abstract
T-mycoplasmas (Ureaplasma sp.) were isolated from 15 out of 22 pneumonic lungs of calves. Nine of 21 tracheas of the same calves also harbored the same organisms. Mycoplasma bovirhinis was usually isolated simultaneously from the same specimens in smaller numbers. The majority of these calves had been reared on a farm where sporadic enzootic calf pneumonia had been prevalent for years. Forty-three calves and beef cattle without pneumonia harbored no detectable number of T-mycoplasmas in the lung or trachea. Metabolism-inhibiting antibodies to both types of mycoplasmas were detected in sera from dead and affected calves, but not in sera from apparently healthy calves. High titers of antibodies to both bovine viral diarrhea virus and bovine adenovirus type 7 were proved similarly in affected and healthy calves. T-mycoplasmas were considered to play an important role in the occurrence of the lethal type of calf pneumonia.
