The University of Queensland, Queensland Alliance for Agriculture and Food Innovation, St Lucia 4072, Queensland, Australia.
The University of Queensland, School of Veterinary Science, Gatton 4343, Queensland, Australia; Jemora Pty Ltd., P.O. Box 2277, Geelong 3220, Victoria, Australia.
Prev Vet Med. 2016 May 1;127:37-43. doi: 10.1016/j.prevetmed.2016.02.006. Epub 2016 Mar 5.
Bovine respiratory disease (BRD) is the major cause of clinical disease and death in feedlot populations worldwide. A longitudinal study was conducted to assess associations between risk factors related to on-farm management prior to transport to the feedlot and risk of BRD in a population of feedlot beef cattle sourced from throughout the cattle producing regions of Australia. Exposure variables were derived from questionnaire data provided by farmers supplying cattle (N=10,721) that were a subset of the population included in a nationwide prospective study investigating numerous putative risk factors for BRD. Causal diagrams were used to inform model building to allow estimation of effects of interest. Multilevel mixed effects logistic regression models were fitted within the Bayesian framework. Animals that were yard weaned were at reduced risk (OR: 0.7, 95% credible interval: 0.5-1.0) of BRD at the feedlot compared to animals immediately returned to pasture after weaning. Animals that had previously been fed grain (OR: 0.6, 95% credible interval: 0.3-1.1) were probably at reduced risk of BRD at the feedlot compared to animals not previously fed grain. Animals that received prior vaccinations against Bovine viral diarrhoea virus 1 (OR: 0.8, 95% credible interval: 0.5-1.1) or Mannheimia haemolytica (OR: 0.8, 95% credible interval: 0.6-1.0) were also probably at reduced risk compared to non-vaccinated animals. The results of this study confirm that on-farm management before feedlot entry can alter risk of BRD after beef cattle enter feedlots.
牛呼吸道疾病（BRD）是全球饲养场牛群中临床疾病和死亡的主要原因。本研究进行了一项纵向研究，以评估与运输到饲养场之前农场管理相关的风险因素与澳大利亚牛生产区各地来源的饲养场肉牛 BRD 风险之间的关联。暴露变量来自供应牛的农民提供的问卷调查数据（N=10721），这些数据是全国范围内前瞻性研究中包含的人群的一个子集，该研究调查了 BRD 的许多潜在风险因素。因果图用于为模型构建提供信息，以允许估计感兴趣的效果。在贝叶斯框架内拟合了多水平混合效应逻辑回归模型。与断奶后立即返回牧场的动物相比，在饲养场中，在畜栏断奶的动物患 BRD 的风险降低（OR：0.7，95%可信区间：0.5-1.0）。与未先前喂谷物的动物相比，先前喂过谷物的动物（OR：0.6，95%可信区间：0.3-1.1）在饲养场中患 BRD 的风险可能降低。先前接种过牛病毒性腹泻病毒 1（OR：0.8，95%可信区间：0.5-1.1）或曼海姆氏菌（OR：0.8，95%可信区间：0.6-1.0）疫苗的动物也可能与未接种疫苗的动物相比，患 BRD 的风险降低。本研究的结果证实，在进入饲养场之前的农场管理可以改变牛进入饲养场后 BRD 的风险。
