Effect of vaccination of beef cows during gestation on transfer of passive immunity and clinical protection of calves against experimental challenge with BRSV
The bovine respiratory disease complex (BRDC) is the leading cause of death of beef calves older than 3 weeks of age and causes major economic losses to producers (USDA NAHMS Beef Part IV. 2007-2008). The bovine respiratory syncytial virus (BRSV) is an important cause of respiratory disease in young calves. Clinical protection against BRSV provided by vaccination of young calves at different ages and with different levels of maternal antibodies has not resulted in significant reduction of BRDC-associated morbidity and mortality (Theurer et al, J Am Vet Med Assoc, 2015). Clinical protection provided by maternally derived immunity against BRSV has been inconsistent in the literature and could negatively affect the efficacy of vaccination programs in young calves (Ellis et al, Can Vet J, 2014). In contrast, failure in the transfer of passive immunity and rapid decay of colostral antibodies have been suggested as risk factors of pre-weaning beef calf pneumonia (Smith DR, Anim Health Res Rev, 2014). The objective of this study was to determine if vaccination of beef cows during gestation resulted in greater transfer of BRSV-specific maternal immunity and provided prolonged clinical protection of calves against experimental challenge with BRSV.