Economic impacts of Bovine Respiratory Disease and alternative measures for diagnosis in Australian feedlot cattle

Abstract

Bovine Respiratory Disease (BRD) is the primary cause of both morbidity and mortality in the Australian feedlot cattle industry. Current disease detection methods in feedlots rely on subjective assessment of animal condition and behaviour in the pens and then treatment based on diagnostic techniques such as rectal temperatures and lung auscultation. These methods of detection are problematic in that not all affected animals will display elevated temperatures and recognition of these clinical symptoms is often too late or may be overlooked due to the presence of subclinical disease. BRD has significant negative economic and welfare implications for the industry, including reduced animal and carcase performance and consequently there is an increasing need for accurate, fast and objective methods of BRD detection. While aspects of the economic impact of the disease on the Australian feedlot industry have been evaluated, the true economic impact of the disease has not yet been quantified. The objective of the present thesis was to provide a comprehensive analysis of the economic impacts of BRD in feedlot cattle, and to explore alternative ways to diagnose BRD and predict an animal’s BRD disease outcome. The overarching hypothesis of this thesis was that BRD causes significant economic losses to the feedlot industry and there are opportunities to improve BRD diagnosis to reduce such losses. Chapter 2 of the thesis explored the impacts of BRD on animal performance and economic returns. Chapter 3 compared the accuracy of commonly used diagnosis methods against each other. Chapter 4 used latent class analysis to group animals into BRD severity classes based on multiple indicators of BRD. Chapter 5 explored the use of a novel technique blood metabolomics to diagnose BRD. Finally, Chapter 6 evaluated factors, or predictors of BRD that could identify animals at risk of dying due to BRD.