On the dairy the calf is separated from the cow. So why do they still have BVDV problems? The NAHMS Dairy 2007 showed that on large dairies (over 500 head) 95% of dairies are vaccinating for BVD. Heifer vaccination is similar. Of operations testing heifers for PI, 21% of large herds had tested, however, that testing occurs more frequently in the East than in the West, says Dr. Bruce Hoffman, API International.
A survey done by Hoffman and Dr. Tom Shelton, Intervet Schering-Plough, of one western calf ranch and the 35 dairies that contributed calves to it indicated that out of 54,260 calves tested, 149 were confirmed as PI (.27% prevalence). Out of the 40 PIs characterized by type, 5 were Type 2 and 36 were Type 1b. Backtracing of calves revealed that 60% of the dairies had contributed at least 1 PI calf.
In this localized dairy shed, BVD virus still circulates within numerous dairy herds in spite of aggressive vaccination programs, says Hoffman. The suggestion was made to producers to test the dams of positive calves and run bulk or string milk samples to rule out the presence of PI cows in the milking herd.