Table 5.

Results from logistic mixed regression analysis for the detection of BCoV ¹ in nasopharyngeal swab samples in 33 Swiss veal calf farms regarding group size ² and age ³, as well as the interaction between group size and age. Additionally, the regression slope ⁴ for group size is provided for each age class separately.

Parameter	Category	Estimate	Standard Error	z-Value	p-Value
Intercept		−1.14	0.55	−2.07	0.039
Group size 2 Age 3		0.07	0.02	4.01	<0.001
	>100 days	−0.16	0.57	−0.27	0.786
Group size: Age	>100 days	−0.05	0.02	−3.20	0.001
Regression slope for each age class 4
Younger	≤100 days	0.07	0.02	4.01	<0.001
Older	>100 days	0.02	0.01	1.20	0.230

¹ Bovine coronavirus. ² Mean farm-level group size. ³ Dichotomized at >100 days according to bimodal distribution. ⁴ Increase in BCoV-positive swab samples (%) with increasing mean group size.