Reasonable expectations for antibiotics in feedyards

Abstract

Use of the Number Needed to Treat (NNT) statistic allows for evaluation and communication of reasonable treatment outcome expectations in populations. The NNT value for a treatment estimates the number of animals which need to be treated in order to make an outcome difference in 1 animal. Evaluation of negative control studies for bovine respiratory disease suggests that the NNT values in high-risk calves for creating a treatment success, prevention of a mortality, and prevention of a clinical case through treatment for control of BRD are 2, 7, and 5, respectively. These values will obviously vary significantly in different clinical situations, but give reasonable expectations for the use of multiple antimicrobials in different groups of cattle over time.