Population-level effects of risk factors for bovine respiratory disease in Australian feedlot cattle

Hay, K. E., Morton, J. M., Clements, A. C. A., Mahony, T. J. and Barnes, T. S. (2017) Population-level effects of risk factors for bovine respiratory disease in Australian feedlot cattle. Preventive Veterinary Medicine, 140 78-86. doi:10.1016/j.prevetmed.2017.03.001

Author Hay, K. E.
Morton, J. M.
Clements, A. C. A.
Mahony, T. J.
Barnes, T. S.
Title Population-level effects of risk factors for bovine respiratory disease in Australian feedlot cattle
Journal name Preventive Veterinary Medicine   Check publisher's open access policy
ISSN 0167-5877
Publication date 2017-05-01
Year available 2017
Sub-type Article (original research)
DOI 10.1016/j.prevetmed.2017.03.001
Open Access Status Not yet assessed
Volume 140
Start page 78
End page 86
Total pages 9
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Language eng
Abstract Results obtained from a nationwide longitudinal study were extended to estimate the population-level effects of selected risk factors on the incidence of bovine respiratory disease (BRD) during the first 50days at risk in medium-sized to large Australian feedlots. Population attributable fractions (PAF) and population attributable risks (PAR) were used to rank selected risk factors in order of importance from the perspective of the Australian feedlot industry within two mutually exclusive categories: 'intervention' risk factors had practical strategies that feedlot managers could implement to avoid exposure of cattle to adverse levels of the risk factor and a precise estimate of the population-level effect while 'others' did not. An alternative method was also used to quantify the expected effects of simultaneously preventing exposure to multiple management-related factors whilst not changing exposure to factors that were more difficult to modify. The most important 'intervention' risk factors were shared pen water (PAF: 0.70, 95% credible interval: 0.45-0.83), breed (PAF: 0.67, 95% credible interval: 0.54-0.77), the animal's prior lifetime history of mixing with cattle from other herds (PAF: 0.53, 95% credible interval: 0.30-0.69), timing of the animal's move to the vicinity of the feedlot (PAF: 0.45, 95% credible interval: 0.17-0.68), the presence of Bovine viral diarrhoea virus 1 (BVDV-1) in the animal's cohort (PAF: 0.30, 95% credible interval: 0.04-0.50), the number of study animals in the animal's group 13days before induction (PAF: 0.30, 95% credible interval: 0.10-0.44) and induction weight (PAF: 0.16, 95% credible interval: 0.09-0.23). Other important risk factors identified and prioritised for further research were feedlot region, season of induction and cohort formation patterns. An estimated 82% of BRD incidence was attributable to management-related risk factors, whereby the lowest risk category of a composite management-related variable comprised animals in the lowest risk category of at least four of the five component variables (shared pen water, mixing, move timing, BVDV-1 in the cohort and the number of animals in the animal's group-13). This indicated that widespread adoption of appropriate interventions including ensuring pen water is not shared between pens, optimising animal mixing before induction, timing of the animal's move to the vicinity of the feedlot, and group size prior to placing animals in feedlot pens, and avoiding BVDV-1 in cohorts could markedly reduce the incidence of BRD in medium-sized to large Australian feedlots.
Formatted abstract
• Population-level effects of risk factors for BRD in feedlot cattle were determined.
• Risk factors with large effects were shared pen water, breed, mixing and move timing.
• BVDV in the pen, prior group size and weight had moderate or modest effects.
• 82% of BRD incidence was attributed to management-related risk factors.
Keyword Bovine respiratory disease
Risk factors
Population attributable fraction
Population attributable risk
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

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