Table 4 Estimated hazard ratio from the multivariable Cox regression model with time of cystic ovarian disease (COD) diagnosis between day 40 and 146 in lactation and herd as cluster

COD recorded during previous lactation

No

510,565

-

1.0

Yes

1,092

364.3

7.5 (6.1 - 9.3)

Interaction parity and calving season

1^st and spring

35,969

-

1,0

1^st and summer

45,126

24.7

2.1 (1.6 - 2.8)

1^st and autumn

64,667

44.8

2.6 (1.9 - 3.4)

1^st and winter

40.776

11.0

1.7 (1.2 - 2.3)

2^nd and spring

32.530

7.3

1.6 (1.1 - 2.2)

2^nd and summer

31,007

72.4

3.5 (2.6 - 4.7)

2^nd and autumn

43,755

168.8

6.1 (4.6 - 7.9)

2^nd and winter

29,121

85.7

3.9 (2.9 - 5.2)

> 2^nd and spring

50,802

43.5

2.6 (2.0 - 3.4)

> 2^nd and summer

45,134

148.4

5.5 (4.2 - 7.3)

> 2^nd and autumn

56,931

300,0

10.2 (7.8 - 13.2)

> 2^nd and winter

32,840

146.1

5.5 (4.1 - 7.2)

Herd size

< 35

430,962

15.8

1.4 (1.2 - 1.6)

35 to 84

75,430

-

1.0

> 84

5,265

7.7

2.0 (1.2 - 3.3)

Region

< 60° latitude

131,159

-

1.0

60 to 65 °

329,186

21.6

1.3 (1.2 - 1.5)

> 65 °

51,312

6.1

1.2 (1.0 - 1.4)