Table 11.

Associations between pen-level prevalence of deep nasopharyngeal culture and susceptibility (C/S) results at 1DOF and 13DOF and pen C/S prevalence at time of BRD treatment.

Risk factor: increase in	Outcome: pen prevalence		95% CI
Pen-level C/S prevalence	C/S at BRD treatment	OR	Lower	Upper	p-value
Prevalence at 1DOF	BRD ≤ 13DOF
M. haemolytica (5%)	M. haemolytica	1.2	0.8	1.9	0.40
P. multocida (5%)	P. multocida	0.5	0.2	1.0	0.04
H. somni (5%)	H. somni	1.4	0.7	2.7	0.37
Any AMR (5%)*	Any AMR	5.6	2.1	15.3	0.0008
Macrolide resistance (5%)*	Macrolide resistance	975	33	29,439	<0.0001
Tetracycline resistance (5%)*	Tetracycline resistance	3.4	1.5	7.6	0.003
Prevalence at 1DOF	BRD ≤ 45DOF
M. haemolytica (50%)	M. haemolytica	1.3	0.9	1.8	0.19
P. multocida (50%)	P. multocida	0.7	0.5	1.0	0.067
H. somni (50%)	H. somni	1.1	0.6	2.1	0.67
Any AMR (50%)	Any AMR	1.8	0.3	9.7	0.49
Macrolide resistance (5%)*	Macrolide resistance	22	1.8	263	0.02
Tetracycline resistance (5%)*	Tetracycline resistance	11	5.4	23	<0.0001
Prevalence at 13DOF	BRD > 13DOF
M. haemolytica (5%)	M. haemolytica	1.4	1.2	1.7	<0.0001
P. multocida (5%)	P. multocida	1.2	0.9	1.6	0.26
H. somni (5%)	H. somni	1.1	0.7	1.6	0.69
Any AMR (5%)	Any AMR	1.7	1.4	2.1	<0.0001
Macrolide resistance (5%)	Macrolide resistance	1.3	1.2	1.5	<0.0001
Tetracycline resistance (5%)	Tetracycline resistance	1.8	1.4	2.4	<0.0001

Analysis adjusted for year and metaphylaxis as well as accounting for clustering by pen cohort. n = 1,599 calves at 1DOF and 1,596 calves at 13DOF (N = 16 pens). OR, odds ratio; 95% CI, 95% confidence interval. **Unconditional GEE logistic regression reported: No calves with BRD from 2021/oxytetracycline cohorts had macrolide resistance at time of BRD treatment and no calves from 2021/tulathromycin cohorts had tetracycline resistance at time of BRD treatment.