Bovine Neonatal Pancytopenia (BNP), a bleeding syndrome of neonatal calves, is caused by alloantibodies absorbed
from the colostrum of particular cows. A commercial BVD vaccine is the likely source of alloantigens eliciting BNP
associated alloantibodies. We hypothesized that the rare occurrence of BNP in calves born to vaccinated dams
could be associated with genetic differences within dams and calves. We found that the development of BNP
within calves was a heritable trait for dams, not for calves and had a high heritability of 19%. To elucidate which
genes play a role in the development of BNP we sequenced candidate genes and characterized BNP alloantibodies.
Alloantigens present in the vaccine have to be presented to the dam’s immune system via MHC class II, however
sequencing of DRB3 showed no differences in MHC class II haplotype between BNP and non-BNP dams. MHC class I,
a highly polymorphic alloantigen, is an important target of BNP alloantibodies. Using a novel sequence based MHC
class I typing method, we found no association of BNP with MHC class I haplotype distribution in dams or calves.
Alloantibodies were detected in both vaccinated BNP and non-BNP dams and we found no differences in alloantibody
characteristics between these groups, but alloantibody levels were significantly higher in BNP dams. We concluded that
the development of BNP in calves is a heritable trait of the dam rather than the calf and genetic differences between
BNP and non-BNP dams are likely due to genes controlling the quantitative alloantibody response following vaccination.