Table 1.

Variables used in regression analysis

Variable name	Type	Levels
Dairy farm	Categorical (GEE for clustering)	Herd 1, herd 2, herd 3
Faecal score	Categorical	⩽2, 3 (ref.), ⩾4
Hygiene score	Categorical	⩽2 (ref.), >2
Body condition score	Categorical	<2, 3 (ref.), >3
Cow contact	Continuous	n.a.
Parity	Categorical	1, 2, ⩾3
Calving ease	Categorical	⩽2 (ref.), >2
Days in milk	Continuous	n.a.
Vaccine use (SRP, HBS)	Dichotomous	0, 1
Ionophore use	Dichotomous	0, 1
Disease	Categorical based on disease type; dichotomous	1–18 vs. 0; 0, 1
Treatment type	Categorical based on treatment type; Categorical based on treatment class	1–8 vs. 0; Antibiotic treatment, other treatment, vs. never treated
Any disease or treatment	Dichotomous	0, 1
Average temperature (°F)	Continuous	n.a.
Average humidity (%)	Continuous	n.a.
Amount of precipitation (inches)	Continuous	n.a.

GEE, Generalized estimating equations; SRP, Salmonella siderophore receptor and porin; HBS, haemorrhagic bowel syndrome; n.a., not applicable.