Calves were block randomized into 1 of the 3 experimental groups in groups of 3 animals based on birth order. spcifiques en anticorps contre le virus respiratoire syncitial bovin (BRSV) et lherpsvirus bovin (BHV) chez des bovins dembouche de lOuest canadien vaccins en primo-vaccination et en rappel de manire homologue ou htrologue. Les maladies respiratoires bovines (BRD) sont une cause conomiquement importante de morbidit et de mortalit chez les veaux dembouche. La maitrise des BRD fait appel le plus souvent une vaccination ? homologue ? utilisant le mme vaccin injectable de virus vivant modifi (MLV) pour la primo-vaccination et le rappel. La primo-vaccination et le rappel htrologue utilisent diffrentes voies et formes antigniques pour lamor?age et le rappel. Trois protocoles de vaccination furent compars : un groupe MLV injectable (IJ) (IJ-MLV) (amor?age avec IJ-MLV environ 48 jours et rappel avec IJ-MLV au sevrage). Un groupe MLV intranasal (IN) (IN-MLV) (amor?age intranasal avec MLV environ 24 heures, deux rappels avec IJ-MLV), et un groupe avec un vaccin intranasal de virus tu (IN-KV) (amor?age avec IN-MLV environ 24 heures, deux rappels avec IJ-KV). Les concentrations danticorps sriques dtermines par preuves immuno-enzymatiques (ELISAs) furent compares et le groupe IN-KV avait des concentrations danticorps spcifiques contre BRSV significativement plus leves aprs le rappel comparativement aux deux groups homologues. Aucune diffrence dans les concentrations danticorps spcifiques contre le BHV ne furent observes entre les groupes. (Traduit par Dr Serge Messier) Introduction Veterinarians and producers vaccinate calves to prime their immune systems against pathogens associated with bovine respiratory disease (BRD) and as one method to manage the impact of the disease. Commonly used viral vaccines contain modified-live viruses (MLV) including bovine respiratory syncytial virus (BRSV), bovine herpes virus type 1 (BHV1), bovine parainfluenza virus 3 (BPIV3), and bovine viral diarrhea virus types 1 and 2 (BVDV1 and 2) (1). Bovine respiratory syncytial virus, BHV1, and BPIV3 target respiratory epithelia and are directly associated with respiratory disease development. Bovine viral diarrhea virus types 1 and 2 are included in the vaccines due to the virus ability to suppress the animals immune system (2). Attesting to the validity of this approach, a recent meta-analysis of the impact of vaccination on feedlot calf BRD morbidity E7080 (Lenvatinib) and mortality indicated that vaccinating for viral pathogens resulted in a protective effect, reducing both morbidity and mortality (3). However, despite the adoption of routine vaccination, BRD still has a negative economic impact on cattle feeding operations across North America through calf morbidity and mortality, and production losses (1,4). The less than optimal effectiveness of vaccination Gata1 in commercial settings may in part be due to how vaccines are applied, including factors E7080 (Lenvatinib) such as vaccination in the face of maternal antibodies (IFOMA) and at the time of stress associated with weaning. Improper application is partly due to timing of the priming dose of vaccine; most producers vaccinate neonatal calves when it is convenient to handle cattle at spring turnout, when the calves are approximately 2 mo old (5). Administration of injectable immunogens to calves is one of the most common methods of vaccination in cow-calf operations; initial priming being the intention (5). The priming vaccine dose is frequently applied when calves are ~2 mo of age, followed by a booster at ~6 mo of age (5). However, at 2 mo of age calves with good passive transfer will E7080 (Lenvatinib) still have high maternal antibody concentrations (6), and maternal antibodies can interfere with the immune systems ability to respond to.