Nonsteroidal anti-inflammatory drug therapy for neonatal calf diarrhea complex: Effects on calf performance

Todd, C. G.; Millman, S. T.; McKnight, D. R.; Duffield, T. F.; Leslie, K. E.

The Kaplan-Meier survival function estimates for time to starter consumption show that MEL-treated calves began consuming starter ration earlier than PLA-treated calves (Figure 1 ). The median time to starter consumption for the MEL-and PLA-treated calves was 12 and 17 d, respectively. The Wilcoxon test indicated that the survival functions for time to starter consumption for the MEL-and PLA-treated calves were different (χ 2 = 8.55; P < 0.01). A Cox proportional hazards model for time to starter consumption, stratified by treatment and controlling for the effects of farm of origin, arrival BW, and age at treatment, was constructed. On any given day after the onset of diarrhea, the probability that MEL-treated calves had begun consuming starter ration was 3.19 times greater than the probability for PLA-treated calves (hazard ratio = 3.19; P < 0.001). Two PLA-treated calves died before fulfilling the starter consumption criteria and, accordingly, were censored from this analysis. The log cumulative hazard plot for time to starter consumption tended to support the assumption of proportional hazards because the curves were parallel along the sections that included the most observations. A mixed model for rate of starter ration consumption was constructed, and the model residuals indicated that starter intake was increasingly more variable over time. Thus, a heterogeneous first-order autoregressive correlation structure was applied to account for the temporal dependence in the starter ration intake measurements. An interaction between treatment and time was included in the final model. As such, starter ration consumption was stratified by week and least squares means were generated. After satisfying the starter consumption criteria, the MEL-treated calves consumed starter ration at a faster rate than PLA-treated calves (P < 0.001; Table 2 ). However, statistical differences for starter ration consumption by time were observed only during wk 5 (P < 0.001; Table 2 ). Over the course of the 8-wk study period, treatment with MEL was associated with significantly improved total starter ration intake, with MEL-treated calves consuming 12.2 kg more starter ration than PLA-treated calves (39.5 and 27.3 kg, respectively; P < 0.01).