Table 5. The odds ratio for infection with B. bigemina, at 95% confidence intervals (CI).

Risk factor Level Odds ratio 95% CI P value AEZ Grazing system       Lowland Fenced 0.57 .19–1.6 0.05 Lowland Free range 2.89 1.36–6.23**   Lowland Tethered 1.01 .29–3.42   Lowland Zero grazing 2.31 .71–8.17   Midland and upland Fenced 1.32 .53–3.32   Midland and upland Free range 2.41 .71–9.21   Midland Tethered 1.13 .42–3.06   Midland Zero grazing 0.54 .23–1.25   Upland Tethered 2.41 1.06–5.53**   Upland Zero grazing 1 –   Age group (months)         0–3   0.46 .25–.82* 0.05 4–12   0.33 .21–.54*   13–18   0.3 .33–2.15   >18   1 –

* Low risk of infection ** High risk of infection