Treating respiratory disease in feedlot cattle (Proceedings)
Respiratory disease is cited as the most common health problem encountered in U.S. feedlots. Bovine Respiratory Disease (BRD) is a multi-factorial disease that affects the lower respiratory system. There are a multitude of viruses and bacteria that can potentially contribute to BRD. However, there are typically one or more predisposing factors that allow pathogens optimal access to the lower respiratory tract. Stress from weaning, transportation, castration and/or dehorning, nutrition and ration changes, enteric disease, immunity, ventilation and weather changes contribute to the onset of BRD.
Metaphalactic treatment protocols are used for "high risk" calves during initial processing upon arrival at the feedlot. A typical pen of high risk calves in the U.S. are Southeastern calves who have originated from multiple herds, have no prior vaccination history, and have been shipped a long distance to the feedlot. Often these stressed calves will already be in initial stages of BRD during transit to the feedlot.
Sick calves should be pulled as they are identified to be morbid and treated with a parental antibiotic. Ancillary treatments such as vitamins or anti-inflammatories are rarely used as there is no evidence that they decrease treatment success or performance. With the advent of long acting antibiotic formulations, most cattle are returned to their pen immediately after treatment instead of convalescing in a hospital pen. Many veterinarians are now recommending treatment moratoriums with antibiotic formulations of 3 to 8 days depending upon drug. Since antimicrobial resistance is not as critical as the antibiotic being able to adequately penetrate diseased lung, treating with more or different drugs following initial treatment is often not beneficial. The stress of pulling from pen and treating is probably worse than benefit of treating with additional drugs. Remember that the primary goal of any respiratory treatment program is to keep the calf alive long enough for the calf's immune system to clear the infection with the assistance of targeted and appropriate antibiotics