Field Monitoring of Colostral BVDV-, BoHV-1-, and BRSV-Specific Serum Antibody Levels in Dairy Calves from Birth to Weaning Fed with Pasteurized Colostrum Pools Obtained from Vaccinated Dams

<b>Background/Objectives</b>: This study aimed to determine the changes in BVDV (bovine viral diarrhea virus), BoHV-1 (bovine herpesvirus-1), and BRSV (bovine respiratory syncytial virus) antibody levels until weaning in calves who ingested colostrum from vaccinated dairy cattle. Additionally, it aimed to measure the antibody levels induced by the vaccine administered before and after socialization after weaning. <b>Methods</b>: Exposure to respiratory viral and bacterial agents was monitored by PCR analysis using nasal swabs at regular intervals from birth to weaning (pre-colostral and after the 2nd, 7th, 15th, 25th, 35th, 45th, 55th, and 65th days). The levels of colostral BVDV, BoHV-1, and BRSV antibodies were monitored using an enzyme-linked immunosorbent assay (ELISA) at the same intervals from birth to weaning (pre-colostral and after the 2nd, 7th, 15th, 25th, 35th, 45th, 55th, and 65th days). <b>Results</b>: The highest level of maternal antibodies in the blood was detected on day 7. BoHV-1, BVDV, and BRSV antibody levels decreased steadily until weaning by 69.14%, 38%, and 53%, respectively. <b>Conclusions</b>: Vaccination strategies should be planned by considering the presence of maternally derived antibodies and minimizing stress that may negatively affect vaccine titers, thus maximizing vaccine efficacy in calves.