Within the fed cattle industry, respiratory disease is still the number one health concern . Acute interstitial pneumonia (AIP, also known as pulmonary edema and emphysema, atypical interstitial pneumonia) is one of the more costly respiratory diseases . The economic costs of the disease are quite high in cattle because the majority of cases develop close to harvest and are usually fatal. A common factor in the pathogenesis of this disease in ruminants has been established. It is precipitated by the ruminal degradation of Ltryptophan, a common amino acid in lush forages and feed grains, to 3-methyl indole (3-MI) . It is absorbed, and in high enough concentrations its metabolites cause damage to pulmonary alveolar cells and AIP can develop. In feedlot cattle being fed a high grain diet 3-methyl indole has been targeted as the causative agent of feedlot AIP, but past research has demonstrated inconsistent results . The amount of ltryptophan in high grain diets may not be high enough to create enough 3-MI to be toxic, leading the field to consider the cause of feedlot AIP to be multifactorial .