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Table 2 Culling - characteristics of the study population (n = 644) and univariable analysis

From: Impact of foot-and-mouth disease on mastitis and culling on a large-scale dairy farm in Kenya

Variable

Total population

Culling

 

N

(col %)

Rate per 1000 cattle-months (95% CI)

HR (95% CI)

P -value

FMD

     

Yes

400

62.1

14.4 (11.2, 18.6)

2.2 (1.3, 3.7)

0.005

No

244

37.9

6.6 (4.1, 10.6)

  

Age (quintiles) a

     

−28- <227d

128

19.9

5.0 (2.4, 10.5)

1.6b (1.3, 1.9)

<0.0001

227- < 577d

129

20.0

2.0 (0.66, 6.3)

577- < 974d

129

20.0

12.6 (7.8, 20.3)

974- < 1363d

129

20.0

17.1 (11.2, 25.9)

1364-3543d

129

20.0

23.2 (15.9, 33.8)

Parity

     

0

381

59.2

4.8 (3.1, 7.4)

1.5b (1.3, 1.8)

<0.0001

1

138

21.4

27.1 (19.5, 37.8)

2

77

12.0

11.6 (6.1, 22.4)

3

29

4.5

36.8 (19.2, 70.7)

≥4

19

3.0

18.2 (5.9, 56.6)

Days in milk

     

Pre-lactating

373

57.9

4.9 (3.1, 7.6)

1.7b (1.5, 1.9)

<0.0001

Early-lactation (<0-100d)

107

16.6

15.2 (9.3, 24.9)

Mid-lactation (101-250d)

85

13.2

18.8 (11.3, 31.2)

Late-lactation (>250d)

44

6.8

25.4 (13.7, 47.2)

Dry

35

5.4

46.0 (27.7, 76.3)

Breed

     

100% Exotic breed

551

85.6

11.5 (9.0, 14.6)

0.7b (0.6, 1.3)

0.52

<25% Indigenous

53

8.2

14.6 (7.3, 29.2)

25% Indigenous

28

4.4

3.7 (0.5, 26.0)

50% indigenous

12

1.9

8.8 (1.2, 62.7)

  1. aNegative values reflect animals born during the outbreak period bIncluded as linear variables based on likelihood ratio tests.
  2. Univariable analysis examines putative associations with the primary outcome (culling) for cattle present during an outbreak of foot-and-mouth disease (FMD) on a dairy farm in Nakuru County, Kenya. Culling is defined as exiting the herd due to any disease or death. HR = Hazard ratio.