Table 1.

Adjusted odds ratios (OR) and 95% CI for milking unit kick-off in primiparous versus multiparous (reference) cows by period of time¹

Time period (DIM)	OR	95% CI	P-value
Overall (3–90)	2.07	1.58–2.73	<0.0001
3–7	1.57	1.07–1.22	0.0202
8–14	2.05	1.50–2.81	<0.0001
15–21	2.74	2.00–3.74	<0.0001
22–28	2.62	1.88–3.65	<0.0001
29–35	2.48	1.81–3.41	<0.0001
36–42	2.22	1.54–3.19	<0.0001
43–49	1.79	1.23–2.59	0.0023
50–56	1.86	1.27–2.74	0.006
57–63	1.41	0.94–2.13	0.1
64–70	2.53	1.73–3.71	<0.0001
71–77	1.71	1.11–2.62	0.014
78–84	1.98	1.29–3.03	0.0016
85–90	2.09	1.42–3.08	0.0002

¹Models were fitted for each of the time periods in analysis. The statistical models included parity (primiparous; multiparous), season of calving, and calving difficulty as fixed effects. Interactions tested were not significant and were removed from the models.