Antibody titer against bovine respiratory syncytial virus in colostrum-feddairy 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 i n 8 dairy herds. Procedure-A standard ELISA was used to determine BRSV-specific antibodies-i n serum:samples obtained monthly, and antibody titers for calves born in va rious 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 general ly 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 dif fer. Conclusions and Clinical Relevance-Calves born in winter generally have low er BRSV-specific antibody titers, which may be caused by generally lower an tibody titers in colostrum or by factors influencing colostrum intake.