Effects of diclofenac sodium and tilmicosin on cardiac biomarkers in calves with bovine respiratory disease complex

This study aimed to evaluate the cardiotoxic potential of diclofenac sodium (DKFS) and tilmicosin (TIL), administered individually or in combination, in calves affected by bovine respiratory disease complex (BRDC). Although both drugs are widely used in BRDC protocols, limited data exist regarding their cardiac safety in cattle. Forty clinically diagnosed BRDC calves were randomised into four groups receiving either oxytetracycline alone (control), or in combination with DKFS, TIL, or both. Blood samples were collected at baseline (0 h), 8 and 24 h after treatment to measure cardiac and hepatic biomarkers, including heart-type fatty acid-binding protein (H-FABP), cardiac troponin I (cTn-I), aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH) and creatinine. Elevated H-FABP and cTn-I levels-particularly in the DKFS + TIL group-suggested early-stage subclinical myocardial injury. Increases in AST, ALT and LDH further indicated additive hepatocellular and myocardial stress. Serum creatinine and haematological parameters remained unchanged. These findings provide biochemical evidence that concurrent administration of DKFS and TIL can induce early myocardial damage without overt clinical signs. Monitoring of cardiac biomarkers may serve as a useful tool for detecting drug-induced cardiotoxicity in veterinary settings. Caution is advised when using DKFS and TIL together in BRDC-affected calves.