It’s one of the most common causes of illness in Australian feedlot cattle but now researchers are a step closer to developing a blood test that will enable efficient and objective diagnosis of Bovine Respiratory Disease (BRD).
Diagnosis of BRD is currently based on visual symptoms such as breathing difficulty, nasal and ocular discharge and lethargy, followed by temperature measurements to trigger treatment protocols.
Meat & Livestock Australia, in consultation with the Australian Lot Feeders’ Association, are funding the research project, Metabolomics of Bovine Respiratory Disease, to develop a blood test to identify BRD using a diagnostic tool known as metabolomics.
MLA Project Manager – Feedlot Joe McMeniman said preliminary results from the research project showed a high degree of accuracy in identifying the disease.
“The researchers set out to explore changes that occur in the blood composition of animals with the onset of disease in the search for biomarkers to objectively define BRD cases,” Dr McMeniman said.
The project is being led by Associate Professor Luciano González from University of Sydney, who said research had confirmed that BRD could be identified using metabolomics, which is a field of science examining the metabolite profile of body tissues and fluids.
“We worked with a commercial feedlot in NSW and the trial involved 898 head of cattle, reflecting a mix of different breeds from different backgrounds,” Associate Professor González said.
PhD student Claudia Blakebrough-Hall explained the methodology.
“We took blood tests at induction and then again any time an animal was identified by pen riders as showing visual signs of BRD,” Claudia said.
“Cattle with visual symptoms were removed from the pen, and for every sick animal pulled, a visually healthy animal was also removed so we could compare blood results, lung auscultation scores determined using a stethoscope, and rectal temperatures.”
The project examined blood samples from both sick and healthy animals to discover informative biomarkers.
Researchers identified 12 different biomarkers in total that were associated to different clinical observations, but were able to determine a sick animal in the early stages of the illness with 85 per cent accuracy. This was completed using just one biomarker on independent datasets which were not used in the initial search of biomarkers.
All animals were followed throughout the supply chain to slaughter, to measure the incidence of lesions, adhesions and abscesses in the lungs to see if there was any evidence an animal had BRD. Other carcase information was also collected.
“The trial demonstrated that when cattle became sick, it changed their metabolites in ways we expected. The composition of the blood of sick cattle reflected the visual changes the pen riders observed,” Claudia said.
Associate Professor González said there was scope to undertake more research that could possibly lead to the development of a simple crush-side test to help lot feeders diagnose BRD.
Future research will map changes in the metabolome from infection to early, mid and late stages of the disease process.
