BRD treatment failure: clinical and pathologic considerations.

In cattle treated for respiratory disease, resolution of clinical signs has been the mainstay of determining treatment response and treatment efficacy. Through the use of calf lung ultrasound, we have found that pneumonia can persist or recur in the face of antibiotic therapy, despite improved clinical signs, leading to greater risk of clinical disease and more antibiotic use in the future. This review will discuss the pros and cons of using clinical signs to define resolution of disease and discuss how to implement lung ultrasound to improve our ability to accurately measure the impact of antibiotic therapy in cattle with respiratory disease.