Table 2.

The potential risk factors for exposure to BRD pathogens (as reflected by S/P ratio (for BHV-4, BVDV, H. somni), PP value (for BRSV, BPI3V, BCoV) and S/N ratio (BHV-1)) which were included in the univariable analysis

Risk factor type	Details
Intrinsic risk factors	Calf breed (Jersey or Friesian)
	ZST score on arrival
	Arrival age
	Arrival weight
Management risk factors	Pen to which the animal was assigned (n = 4)
	Nutrition plane (high, medium or low)
	UFL (unité fourragère lait) intake in the pre-weaning period (d-56 to d-14)
	Percentage of UFL allowance consumed in pre-weaning period (d-56 to d-14)
	Average daily gain in pre-weaning period (d-56 to d-14)
Clinical risk factors	Maximum temperature recorded during the pre-weaning period (d-56 to d-14)
	Mean temperature recorded during the pre-weaning period (d-56 to d-14)
	Maximum respiratory score in the pre-weaning period (d-56 to d-14)
	Number of times treated for BRD in pre-weaning period (d-56 to d-14)
	Number of sickness bouts recorded in the pre-weaning period (d-56 to d-14)
	Total white blood cell count at d − 14
	Lymphocyte count at d − 14
	Haptoglobin level at d − 14
	H. somni S/P at d − 14
	BHV-4 S/P at d − 14
	BVDV S/P at d − 14
	BHV-1 S/N at d − 14
	BPI3V PP at d − 14
	BRSV PP at d − 14
	BCoV PP at d − 14

The pre-weaning period was from d − 56 to d − 14 relative to weaning at d 0. Note that BRD pathogen S/P ratios, S/N ratios or PP values at d − 14 were not considered as risk factors for changes in antibody levels for that specific pathogen during the peri-weaning period (d − 14 to d 14)