B.FLT.0246 Impact of subclinical bovine respiratory disease

Summary

Bovine respiratory disease (BRD) is the most prevalent and costly disease of Australian feedlot cattle. Research conducted in the United States reports that cattle with lung abnormalities have decreased carcase weight and fatness (including marbling). However, up to 50 % of cattle with lung abnormalities at slaughter exhibit no clinical signs of BRD during the feeding period. No peer reviewed data is available on the subclinical incidence of BRD of Australian feedlot cattle.


This study collected records on 1274 cattle inducted to a commercial feedlot during 2017. The cattle were monitored during the feeding period and all production and animal health data were collected in both the live animal and at the carcase level.


A key result of the study is that BRD treatment in the feedlot did not have a significant association with the disease classification in the carcase or on carcass traits. This may be due to a number of reasons, such as the treated animals fully recovering, animals having pre-existing lung damage upon entry to the feedlot, or some animals maintaining a sub clinical status during the feeding period and so not receiving a treatment. It may also be plausible that there was a poor accuracy of BRD diagnosis which would lead to a poor association between treatment records and gross pathology.


Induction weight had a positive effect on disease outcome. The trend was that heavier induction weights resulted in less disease being recorded at the carcase level. There was a trend that prevaccination of cattle prior to feedlot entry reduced disease outcome in the carcase but it was not significant. Hot Standard Carcase Weight (HSCW), Average Daily Gain (ADG) and Carcase Fat Depth (P8) were all significantly affected by Breed and Induction weight and combined disease classification in the carcase. HSCW was significantly lower in cattle that had a severe disease classification compared to a normal or moderate classification.