Antibody titer against bovine respiratory syncytial virus in colostrum-fed dairy calves born in various seasons

Objective-To determine antibody titer against bovine respiratory syncytial virus (BRSV) in dairy carves on farms and to investigate-whether passively acquired antibody titers differ in calves born in various seasons. Sample Population-Serum samples from 129 colostrum-fed replacement calves in 8 dairy herds. Procedure-A standard ELISA was used to determine BRSV-specific antibodies-in serum:samples obtained monthly, and antibody titers for calves born in various seasons were compared. Results-BRSV-specific antibody titer incolostrum fed dairy calves decreased to undetectable values-at 3 to 4 months old. Calves born in winter generally had lower titers, compared with those for calves born in other seasons (P < 0.05). Titers in calves born in sea; sons other than winter did not differ. Conclusions and Clinical Relevance-Calves born in winter generally have lower BRSV-specific antibody titers, which may be caused by generally lower antibody titers in colostrum or by factors influencing colostrum intake.