Table 5

Model 3.

Variable

n

Coefficient

SE

p

CI^a

OR

CI^b

Intercept

2.85

0.16

Age category

8 weeks

24

reference

14 weeks

24

1.47

0.14

< 0.01

1.19

1.75

23.57

11.32

49.06

Gilts

25

1.52

0.15

< 0.01

1.23

1.81

26.31

11.99

57.74

Parity 1

25

1.36

0.15

< 0.01

1.07

1.65

13.37

6.14

29.11

Parity 2

25

1.52

0.15

< 0.01

1.22

1.81

22.81

10.39

50.05

Parity 3

24

1.6

0.15

< 0.01

1.3

1.9

29.93

13.32

67.25

Parity 4

24

1.38

0.15

< 0.01

1.09

1.68

17.98

8.21

39.37

Parity 5+

24

1.42

0.15

< 0.01

1.13

1.71

14.73

6.75

32.14

Purchased gilts

No

13

Yes

12

-0.61

0.16

< 0.01

-0.92

-0.29

0.35

0.18

0.7

Length of time purchased stock isolated

Not isolated

14

reference

1–5 days

3

-0.36

0.25

0.14

-0.85

0.12

0.61

0.21

1.77

6 days or more

8

-0.46

0.18

< 0.01

-0.81

-0.11

0.43

0.2

0.93

Pig free time for visitors

< 48 hours

17

reference

≥ 48 hours

8

-0.44

0.18

< 0.05

-0.79

-0.1

0.44

0.2

0.93

Estimation of random effects:

Variation between herds

0.11

0.04

Variation between pens

0.2

0.03

Variation between pigs

0.45

0.02

Multivariable three level mixed model of factors associated with log IRPC of 1184 pigs belonging to 25 herds that had seropositive young stock.

Sample size (n); standard error (SE); probability function (p); 95% confidence interval (CI^a) when pigs' log IRPC (+12) values were used as a continuous outcome variable; Odds Ratios (OR) and 95% confidence interval (CI^b) when pig-level seropositivity (absence/presence of antibodies) was used as a comparative binary outcome variable (exp(coefficient+/-(1.96 × standard error))).

Evans et al. BMC Veterinary Research 2008 4:48   doi:10.1186/1746-6148-4-48