Factors affecting costs for on-farm control of salmonella in Swedish dairy herds

Table 4 Results from regression analysis of factors affecting costs for salmonella control in Swedish dairy herds

Random effects:
Group	Variance	Std Dev
Year	0.28	0.53
County	0.10	0.31
Residual	0.88	0.93
Fixed effects:
Variable	Category	Estimate	Std Error	t-value	p-value
Intercept		0.85	1.16	0.73	0.46
Herd size		1.37	0.20	6.71	<0.001
Restriction period		0.95	0.19	5.02	<0.001
Serotype	Dublin	Ref level	-		-
	Typhimurium	0.38	0.29	1.27	0.21
	Reading	0.18	0.61	0.29	0.77
	Other^a	0.80	0.43	1.86	0.07
Administrative change at SBA	1999–2008	Ref level	-		-
	2009–2013	0.24	0.45	0.55	0.59

A mixed linear model was used. County and year restrictions were initiated were included as random effects. All numerical variables were log-transformed in the model. All factors of interest where data were available were included and kept in the model, although some did not show a significant association with the outcome
^a“Other” included seven serotypes with one or two observations each

ISSN: 1751-0147