RESUMO
This study was designed to compare morbidity and mortality due to bovine respiratory disease (BRD) in 1,400 ranch-fresh, northern US calves that received either no metaphylaxis (MTX) (Group 1), MTX prompted by pen morbidity (Group 2), MTX prompted by a decline in feed intake (Group 3), or on-arrival MTX (Group 4). Ceftiofur crystalline free acid (6.6 mg/kg) was the MTX antimicrobial used. Decreased feed intake did not meet the study threshold, so Groups 1 and 3 were combined into a single control group. The percentage of calves not treated for BRD was 14% to 15% higher in Groups 4 and 2 (72.7% and 73.4%, respectively) compared with the controls (58.2%; P ≤ .02). Mortality was numerically higher in Group 2 (3.4%) compared with Groups 4 and 1 (0.9% and 1.6%, respectively). There were no differences in average daily gain or feed consumption. In northern, ranch-fresh calves, MTX as a health management practice reduces the incidence of BRD and has better utility when performed on arrival versus relying on morbidity as a signal for antimicrobial administration.
