Table 2.

Potential risk factors for positive swab sample test for bovine coronavirus (BCoV) in Swiss veal calves from 33 farms.

Level	Category	Description
Potential farm-level risk factors	Management	Number of calves fattened annually; mean group size; stocking routine (continuous/all-in-all-out); barn capacity 1; physical contact among calves of neighboring pens (yes/no); shared air space among pens (yes/no); total number of birth farms 2; number of birth farms per ten purchased calves; refusing sick calves upon arrival (yes/no); median duration of the fattening period; median average daily weight gain; median carcass weight; slaughter weight; disinfection of pens after use (yes/no); farm-level mortality rate; unwanted early slaughter (yes/no); access to outdoor pen (yes/no); feeding of CMT-positive milk (yes/no) 3; vaccination against respiratory pathogens (yes/no); TIDDD 4
Potential individual calf level risk factors	Sampled calves	Purchased calf 5 (yes/no); age at purchase (days); age at sampling (days) 6; death before slaughter 7 (yes/no);
	Detection of respiratory viruses 8	Positive test for BRSV, BPI3V, IDV, or ICV (yes/no)
	Detection of respiratory bacteria by culture	Positive culture for Histophilus somni, Bisgaard Taxon 39, Mannheimia haemolytica, Pasteurella multocida, Mycoplasma bovis, or Mycoplasma dispar (yes/no)

¹ Barn capacity: number of calves that can be fattened at the same time on one farm. ² Total number of farms selling calves to respective veal calf farm. ³ CMT: California mastitis test, score 2 or higher [44]. ⁴ Antimicrobial treatment incidence rates in defined daily doses per animal/year (ddd/ay; EMA, 2013, 2016). ⁵ In contrast to calves born at the fattening farm. ⁶ Dichotomized according to bimodal distribution at ≤100 days and >100 days of age at sampling. ⁷ Calf succumbed to disease before slaughter (i.e., mortality on individual level; yes/no). ⁸ BRSV: bovine respiratory syncytial virus; BPI3V: bovine parainfluenza 3 virus; IDV: influenza D virus; ICV: influenza C virus.