1. Changes in the bacterial flora of the upper and lower respiratory tracts and bronchoalveolar lavage differential cell counts in feedlot calves treated for respiratory disease;ALLEN, J.W.; VIEL, L.; BATEMAN, K.G.; ROSENDAL, S.; SHEWEN, P.E.; PYSICKSHEARD, P.;Canadian Journal of Veterinary Research; Practice a JANUARY; Use of transtracheal aspiration to identify pathogens in pneumonic calves,1992