Acute interstitial pneumonia, bovine respiratory disease complex and potential pneumotoxicity in feedlot cattle

A retrospective cohort study was performed to evaluate trends in feedlot mortalities. The study population included 21.8 million cattle placed in 121 feedlots. The overall mortality risk was 1.26%. The risk of feedlot mortalities increased from 1994 through 1999 because of increases in the proportion of animals that died from respiratory disorders.; Case-control studies were performed to evaluate potential causes of AIP. Biological samples were collected from animals in 14 feedlots. Histological findings were categorized as AIP, bronchopneumonia (BP), and controls. The presence of a viral respiratory pathogen was not associated with histological category. Lung 3-methyleneindolenine (3MEIN) concentrations were greater in AIP (P < 0.01) and BP (P < 0.01) cases than controls. Blood 3MEIN-adduct concentrations were greater in AIP-affected animals than controls (P < 0.01) or BP cases ( P = 0.02).; Time-dependant patterns of plasma 3-methylindole (3MI) and blood 3-methyleneindolenine (3MEIN)-adduct concentrations in feedlot cattle were described using 64 steers. Blood samples were collected 4 times per week for 3 weeks, then 3 times per week for 5 weeks, then weekly for 10 weeks. Blood 3MEIN-adduct concentrations peaked during the period of greatest risk for BRD. Plasma 3-methylindole (3MI) concentrations decreased during the same period.; The effect of dietary aspirin and vitamin E on plasma 3MI, blood and lung 3MEIN, lung lesions, and animal performance was evaluated. Two trials were conducted concurrently using 256 steers. Treatments were aspirin (0 or 3 g), and supplemental vitamin E (0 or 1,500 iu). Trial 1 animals were harvested on day 59. Trial 2 animals were harvested on day 138. Treatment was not associated with decreases in blood or lung 3MEIN (P > 0.50). Nor was treatment associated with changes in body weight, mean daily weight gain, dry matter intake, or feed conversion (P > 0.50).; Increased pulmonary generation of the pneumotoxin 3MEIN, may be important in the pathogenesis of AIP. Additionally, 3MEIN-adduct concentrations were elevated during the period temporally associated with greatest risk for BRD.