A field trial, of preshipment vaccination, with intranasal infectious bovine rhinotracheitis-parainfluenza-3 vaccines.

A total of 849 calves, 278 controls, 335 vaccinated intranasally with IBR-PI3/TS and 236 vaccinated intranasally with IBR-PI3/PTC were studied in a field trial of preimmunization. All calves were vaccinated in Saskatchewan at least three weeks prior to shipment to feedlots. Four hundred and twenty six calves were not sold within eight weeks of vaccination; however, seven of these died within four weeks of vaccination. Treatment rates varied from 1.0% to 5.2%. There was no significant effect of vaccination on treatment rates. Similarly, there was no significant effect of vaccination in the 74 calves sold to feedlots in Saskatchewan. Three hundred and forty nine calves were sold to feedlots in Ontario. Two of these died from fibrinous pneumonia. Treatment rates varied from 1.7% to 33.3% in different feedlots, but there was no significant effect of vaccination on treatment rates. Therefore, preimmunization is unlikely to significantly reduce the overall treatment rate in calves entering feedlots.