Whole-Blood Transcriptome Analysis of Feedlot Cattle With and Without Bovine Respiratory Disease.

Janelle Jiminez,Frank Van Der Meer,Karin Orsel,Graham Plastow,Le Luo Guan,Edouard Timsit

doi:10.3389/fgene.2021.627623

Abstract

Bovine respiratory disease (BRD) is one of the main factors leading to morbidity and mortality in feedlot operations in North America. A complex of viral and bacterial pathogens can individually or collectively establish BRD in cattle, and to date, most disease characterization studies using transcriptomic techniques examine bronchoalveolar and transtracheal fluids, lymph node, and lung tissue as well as nasopharyngeal swabs, with limited studies investigating the whole-blood transcriptome. Here, we aimed to identify differentially expressed (DE) genes involved in the host immune response to BRD using whole blood and RNA sequencing. Samples were collected from heifers (average arrival weight = 215.0 ± 5.3 kg) with (n = 25) and without (n = 18) BRD at a commercial feedlot in Western Canada. RNAseq analysis showed a distinct whole-blood transcriptome profile between BRD and non-BRD heifers. Further examination of the DE genes revealed that those involved in the host inflammatory response and infectious disease pathways were enriched in the BRD animals, while gene networks associated with metabolism and cell growth and maintenance were downregulated. Overall, the transcriptome profile derived from whole blood provided evidence that a distinct antimicrobial peptide-driven host immune response was occurring in the animals with BRD. The blood transcriptome of the BRD animals shows similarities to the transcriptome profiles obtained from lung and bronchial lymph nodes in other studies. This suggests that the blood transcriptome is a potential diagnostic tool for the identification of biomarkers of BRD infection and can be measured in live animals and used to further understand infection and disease in cattle. It may also provide a useful tool to increase the understanding of the genes involved in establishing BRD in beef cattle and be used to investigate potential therapeutic applications.

Highlights

Bovine respiratory disease (BRD) is one of the main causes of morbidity and mortality in beef cattle in North America (USDA, 2011)
Heifers received a subcutaneous injection of a long-acting macrolide and were weighed and vaccinated against infectious bovine herpes virus-1 (BoHV-1), bovine viral diarrhea virus (BVDV), bovine parainfluenza-3 (PI3V), bovine respiratory syncytial virus (BRSV), Mannheimia haemolytica, Histophilus somni, and clostridial pathogens
The Average daily gain (ADG) in the NB heifers was considerably higher (P < 0.001) than in the BRD heifers, which on average gained less weight (P < 0.001) from the time they arrived to the feedlot to the time they were enrolled in the study (Supplementary Table 1)

Summary

Introduction

Bovine respiratory disease (BRD) is one of the main causes of morbidity and mortality in beef cattle in North America (USDA, 2011). Beef cattle of all ages can be affected with BRD; they are most affected on or soon after entry into the feedlot (Babcock et al, 2010). This timing of infection is most likely due to the animal’s exposure to a wide range of pathogens that takes place at a time when various stressors (weaning, transportation, and commingling) negatively affect their immune system (Caswell, 2014; Timsit et al, 2016). The host immune response detected in the blood can reflect those responses occurring at the site of infection (Kawayama et al, 2016; Vinther et al, 2016)

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