Breeding for improved resistance to bovine respiratory disease (BRD)

Bovine respiratory disease (BRD) is a multifactorial disease affecting cattle of all ages. Internationally and in Ireland, it represents the most significant cause of bovine morbidity and mortality. Clinical symptoms include coughing, breathing difficulty, eye and nasal discharge, a high temperature and reduced animal performance.

Susceptibility to BRD is moderately heritable and therefore it is possible to breed animals that display improved resistance to BRD. Consequently, genomic research at AGRIC, Teagasc, Grange,  aims to identify the differences in DNA sequences in cattle which may infer resistance to two of the main viruses which cause BRD, bovine respiratory syncytial virus (BRSV) and bovine herpes virus 1 (BoHV1). Two viral challenge experiments were conducted where Holstein-Friesian calves were experimentally challenged with either BRSV or BoHV1. Changes in gene expression in the bronchial lymph node and lung tissues induced by these BRD causing viruses were examined. Increased expression of important immune function genes during the BRSV and BoHV1 infections was found. Additionally, a novel sequencing technique was used to identify regions of open chromatin in the genome regulating the calves’ genetic responses, such as the increase in expression of immune function genes, due to BRSV infection. Chromatin is a complex of DNA and protein found in cells. Chromatin is open and active when it is in an uncondensed state and is accessible to gene regulatory elements. It can then function in regulating gene expression. These identified open chromatin regions will be examined for changes in DNA sequence which impact resistance to BRD that can be used in genomic selection breeding programmes to select healthier, more robust cattle. Breeding healthier cattle, which are more resistance to BRD, through genomic selection programmes (e.g. EBI, Beef Eurostar), will reduce productivity losses and veterinary costs associated with incidents of BRD.

Acknowledgement

This research is funded by a US-DAFM-DAERA partnership tripartite grant (RMIS-0033 Project 16/RD/US-ROI/11) led by Dr. Sinead Waters, and Teagasc research investigators (Dr. Bernadette Earley, Dr. Matthew McCabe), working in collaboration with the University of Missouri, USA (Prof. Jeremy F. Taylor, Prof. JaeWoo Kim) and AFBI, Northern Ireland (Prof. Louise Cosby, Dr. Ken Lemon, Dr. Catherine Duffy, Dr. Michael McMenamy). Dr. Dayle Johnston is employed as a Post-Doctoral researcher on the grant.

Dayle Johnston, Bernadette Earley, Matthew McCabe, Sinead Waters