The aim of this study was to evaluate pulmonary function test, acute phase proteins, pro-inflammatory cytokines, electrolyte balance and electrocardiographic alterations in BRD affected calves compared to pen matched healthy control calves. A total of 30 calves (20 BRD affected calves and 10 apparently healthy calves) were used in this study. The BRD affected calves showed significant (P<0.05) reduction in blood pH, partial pressure of oxygen, oxygen saturation, calcium, phosphorus, magnesium, sodium and chloride, and significant (P<0.05) increase in partial pressure of carbon dioxide, total carbon dioxide and potassium. Acute phase proteins and Proinflammatory cytokines assessment revealed a significant (P<0.05) increase of serum amyloid A, haptoglobin, fibrinogen and interleukin-6 in diseased calves compared to healthy control calves. Electrocardiographic examination of BRD affected calves revealed a significant increase in heart rate with a significant (P<0.05) alteration in ECG wave trace parameters (P wave, QRS complex, T wave, PR interval, QT interval). In conclusion, measurement of pulmonary function test, APPs, cytokines and ECG could be used as valuable and early diagnostic tools for BRD diagnosis in feedlot cattle calves.