Table 7.

Variables in the final model with a significant effect on a dairy free-stall herd’s digital dermatitis status (n=388^b)

Variable	OR	95% CI of OR	P value
Purchase of livestock during the last 5 years a
0 animals	Baseline
1–2 animals	1.53	0.61–3.80	0.364
3–4 animals	1.65	0.53–5.18	0.389
5–11 animals	1.71	0.77–3.78	0.185
12–27 animals	2.30	1.03–5.12	0.042
28–52 animals	4.34	1.71–11.04	0.002
≥ 53 animals	5.39	1.90–15.35	0.002
Missing
Trimming frequency a
1 < 2/year	Baseline
< 1/year	0.41	0.17–0.97	0.043
2 < 3/year	1.58	0.87–2.85	0.130
≥ 3/year	4.09	1.57–10.69	0.004
Certified prof trimmer trims ≥ 90% of cowsa
No	Baseline
Yes	3.98	1.32–11.95	0.014
Cleaning of feet in chute before trimming
No	Baseline
Yes	1.98	1.12–3.51	0.019
Uncertain	0.82	0.31–2.14	0.678
Slatted flooring
Yes	Baseline
No	2.36	1.30–4.26	0.005
Uncertain	1.29	0.48–3.48	0.614
Random effect county (var):	0.568	0.142–2.273

Variables with P < 0.05 in the final multilevel logistic regression model

n number of herds, OR odds ratio, CI confidence interval

^aData from NDHRS ^bOne herd had a missing value for slatted flooring