PSIII-10 - Modified-live Virus Respiratory Vaccines and Bovine Respiratory Disease Influence the Respiratory Microbiome of Cattle

Abstract: Modified-live virus (MLV) respiratory vaccines are commonly administered to beef cattle upon arrival in feedlots to prevent bovine respiratory disease (BRD) but their impact on respiratory microbial communities is unknown. The objective of this study was to evaluate the impact of intranasal and parenteral MLV vaccination and health status on the respiratory microbiome of feedlot cattle with a high-risk of BRD. Crossbred beef calves were blocked by truckload and stratified by arrival body weight, sex, and ranch tag status. Cattle were randomly assigned to 1 of 3 treatment groups: no vaccination, intranasal MLV, or parenteral MLV. Nasopharyngeal swabs were collected on d 0 and 28, and upon treatment for BRD. A subset of these samples (n=600) was selected from an equal number of healthy and morbid cattle among vaccine treatment groups. Additionally, all chronically ill cattle and mortalities were selected for sequencing. After DNA extraction, 16S rRNA gene sequencing was used to characterize the microbiome of the upper respiratory tract. The overall composition of respiratory tract microbial communities in all treatment groups was similar to previously described respiratory communities. Members of the families Pasteurellaceae and Mycoplasmataceae , which include common respiratory pathogens (Mannheimia, Pasteurella, Histophilus, Mycoplasma), were prevalent in all communities. However, the proportions of these important taxa differed between cattle that developed BRD and cattle that remained healthy. Morbid cattle had lower (P< 0.05) phylum members Proteobacteria and higher (P< 0.05) Tenericutes than cattle that remained healthy. Cattle that received an intranasal vaccine had a higher (P< 0.05) abundance of Proteobacteria and lower (P< 0.05) abundance of Tenericutes compared to both control and parenteral cattle. Results indicate that intranasal vaccination had a significant impact on respiratory microbial communities, while parenteral vaccination did not. These results add to our understanding of the impacts of MLV vaccination on the health and productivity of feedlot cattle.