Development of a Bovine Leukocyte Differential index for Australian feedlot cattle

Summary

MLA and Advanced Animal Diagnostics have partnered to investigate the predictive ability of a chute side test to predict bovine respiratory disease (BRD).

The current research explored the ability to predict BRD risk in 2,450 Australian feedlot cattle using Advanced Animal Diagnostics’ QScout® Cattle Lab, a chute-side blood test, which reports total leukocytes, neutrophils, mononuclear cells, eosinophils and neutrophil:mononuclear ratio.

Objectives

Develop a model to predict BRD risk of Australian feedlot cattle based on Bovine Leukocyte differential index and other information available at arrival.

Key findings

• Cattle with low eosinophils at feedlot induction may at a higher risk of developing BRD (approximately 2-fold).
• Biological hypotheses include:
  • stress induced changes in immune cell development
  • the peripheral blood concentration of eosinophils may be less in animals at greater risk for BRD in favour of other leukocytes (i.e., neutrophils) that specialize in viral and bacterial infection, rather than parasitic infection
  • eosinophils in animals at greater BRD risk may be more greatly redistributed from the blood to the lymphatic system or sites of infection to aid in resolving inflammation.
• Further research is required to determine management protocols for these cattle, and the economic viability of utilising the QScout® Cattle Lab technology in Australian feedlots.

Benefits to industry

This project supported early stage research on a rapid immune cell counter. Further research is required to determine if the technology can cost effectively refine antimicrobial use for treatment of BRD.

MLA action

The published report will be distributed to participants of the ALFA-MLA consulting veterinarian and nutritionists meeting.

Future research

Economic modelling of theoretical management strategies for low eosinophil cattle is required.