Pulmonary Emphysema in Newly Weaned Calves

Abstract

Bovine pulmonary emphysema has been recognized in many countries for a number of years. There is confusion as to the cause and the nomenclature of the various diseases of cattle which have pulmonary emphysema as a major lesion. The term "pulmonary emphysema" is used as the name of a disease and as lesion identification, which adds to the confusion. The lung can respond to an irritant in only a few
ways, which allows for lesions to appear similar even though there are different causes. The cause of pulmonary emphysema in newly weaned calves can only be postulated at this time. Circumstantial evidence suggests a relationship to consumption of silage or moldy hay by the calves. Corn silage is more often a major part of the diet in our area. Calves on silage do not have the clinical signs until approximately 4 weeks after weaning and change of diet, so there may be some change in bacterial flora which could change the biochemical constituents of the rumen liquor. On the other hand, there may be some infectious cause such as syncytial virus. Thirdly, the cause may be a combination of biochemical toxin and infectious agent. Only controlled research will resolve the question of etiology.
This paper is not to answer the question of etiology but to emphasize the clinical signs, lesions, relationship to diet and weaning, as well as the economic importance.