Table 3 Multivariable Cox-proportional hazard model, with pen as a shared frailty, to determine covariates of time to poultry layer mortality in the Savannah region of Nigeria

Pen type

Open

Ref

Ref

Ref

Ref

Sealed

0.568 (0.554 - 0.582)

0.007

- 45.660

< 0.001

Season

Cold-dry

Ref

Ref

Ref

Ref

Hot-dry

61.499 (58.836 - 64.283)

1.389

182.360

< 0.001

Warm-wet

12.013 (11.566 - 12.478)

0.232

128.470

< 0.001

Age (weeks)

19 - 38

Ref

Ref

Ref

Ref

39 - 58

0.329 (0.316 - 0.341)

0.006

-57.420

< 0.001

59 - 78

0.032 (0.031 - 0.034)

0.000

-155.070

< 0.001

> 78

0.011 (0.011 - 0.012)

0.000

-180.330

< 0.001

Age (linear)

Nil

0.911 (0.911 - 0.911)

0.000

-206.860

< 0.001

Stocking density (linear)

Nil

1.053 (1.043 - 1.064)

0.005

10.100

< 0.001

Feed consumption (linear)

Nil

1.012 (1.011 - 1.013)

0.000

32.160

< 0.001