Enrollment
The majority of calves came from herds categorized
as large (26% of calves) or very large (53%). Six hundred
seventy-eight calves (24.7%) were vaccinated at 2
wk only, 664 (24.2%) at 5 wk only, 644 (23.4%) at 2 and
5 wk, and 764 (27.8%) were not vaccinated. The unvaccinated
control group contained more calves because on
2 occasions the shipment of vaccines was delayed, and
therefore, all calves were given the saline placebo.