Table 4 Six logistic models for farm-level factors associated with Campylobacter in broilers in Iceland (n = 28a)
Variable | Automated forward selection | Automated forward stepwise | Automated backward selection | Automated backward stepwise | Manual backward selection using "manure spread in summer" | Manual backward selection using "manure spread in winter" |
|---|---|---|---|---|---|---|
Median flock size on farm (divided by 1,000) | 0.10 (0.000)b | 0.10 (0.000) | 0.11 (0.000) | 0.09 (0.001) | 0.13 (0.000) | 0.12 (0.000) |
Farm water source | ||||||
Non-official | Ref. | Ref. | Ref. | Ref. | ||
Non-official treated | -0.57 (0.066) | -0.03 (0.913) | -0.50 (0.169) | -0.33 (0.370) | ||
Official | -0.60 (0.051) | -0.76 (0.009) | -1.04 (0.004) | -0.99 (0.005) | ||
Official treated | -0.87 (0.032) | -1.06 (0.006) | -1.21 (0.006) | -1.17 (0.007) | ||
Other domestic livestock on farm | -0.65 (0.026) | -0.60 (0.028) | -1.01 (0.004) | -0.90 (0.004) | ||
Other commercial poultry on farm | 0.59 (0.000) | 0.59 (0.000) | -0.72 (0.063) | -0.59 (0.097) | ||
Number of houses on farm | 0.06 (0.038) | 0.13 (0.008) | 0.11 (0.008) | |||
Manure spread on fields in winter seasonc | 0.54 (0.035) | 1.90 (0.014) | Not included in model | 0.97 (0.004) | ||
Manure spread on fields in summer seasonc | -1.71 (0.028) | 0.92 (0.025) | Not included in model | |||
Manure stored on farm at any time of year | -0.83 (0.029) | -0.76 (0.025) | ||||
Farm has all-in-all-out policy | ||||||
AICd of model | 5.09 | 5.09 | 4.86 | 4.78 | 4.94 | 4.79 |