Table 10.

Differences in antimicrobial resistance (AMR) patterns from the repeated measures multilevel logistic regression models at 13DOF between years and metaphylaxis administered (year 2020/tulathromycin, year 2021/tulathromycin, and year 2021/oxytetracycline), reported as population-averaged odds ratios (ORs) and 95% confidence intervals (CIs), accounting for clustering at the pen-level. n = 1595 calves for which susceptibility data were available.

AMR Outcome of Interest	Pairwise Comparison of Year/Metaphylaxis	OR	95% CI	p-Value
M. haemolytica tulathromycin	2021/tulathromycin vs. 2020/tulathromycin	0.1	0.03, 0.7	0.02
	2021/oxytetracycline vs. 2020/tulathromycin	0.06	0.01, 0.4	0.004
	2021/oxytetracycline vs. 2021/tulathromycin	0.4	0.05, 3.2	0.39
M. haemolytica gamithromycin	2021/tulathromycin vs. 2020/tulathromycin	0.1	0.03, 0.7	0.018
	2021/oxytetracycline vs. 2020/tulathromycin	0.06	0.01, 0.4	0.004
	2021/oxytetracycline vs. 2021/tulathromycin	0.4	0.05, 3.1	0.39
P. multocida tetracycline *	2021/tulathromycin vs. 2020/tulathromycin **	0.2	0, 0.90	0.08
	2021/oxytetracycline vs. 2020/tulathromycin	15	6.9, 37	<0.0001
	2021/oxytetracycline vs. 2021/tulathromycin **	83	19, ∞	<0.0001

Post-hoc Wald test for significance of differences between year and metaphylaxis options was not different for the recovery of any pathogen with AMR or M. haemolytica with resistance to tildipirosin, tilmicosin, or tetracycline. * Zero calves with tetracycline resistance at 13DOF from year 2021 tulathromycin-treated pens. Exact logistic regression used. ** Median unbiased estimate reported.