Oxytetracycline toxicity associated with bovine respiratory disease therapy

Abstract

Three hundred and forty-two heifer calves were assigned to three treatments; (1) 30 calves exposed to IBR/IPV virus (2) vaccinated against IBR/IPV virus and bovine diarrhoea virus and (3) non vaccinated controls. Treatment groups were housed in separate facilities to prevent spread of disease between groups. Incidence of bovine respiratory disease was 49.1% in exposed calves, 20.2% in vaccinated calves and 14% in controls. Respiratory disease was treated by either high dose (33 mg/kg) or low dose (11 mg/kg) of oxytetracycline (OTC), unresponsive animals were treated with sulfonamides. Of 51 calves treated with low doses of OTC, 25 responded and needed no further treatment, and 4 failed to respond and died. There was no difference in response between treatment groups. Of 45 treated with high doses of OTC 20 failed to respond and died. There was no significant difference in response to treatment with high or low dose OTC between calves fed rations of different calorific value. PM examinations showed lung lesions which ranged in severity from mild bronchopneumonia to severe fibrinous bronchopneumonia. Most pasteurella strains isolated were resistant to tetracyclines and sulfonamides. Diffuse renal tubular epithelial necrosis and tubular casts were seen in 19 of 20 calves that died after high dose OTC.