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BOVINE respiratory disease (BRD) has a major economic impact in different cattle production systems worldwide (Griffin 1997, Pardon and others 2013, Lehenbauer 2014) and is the main reason of antimicrobial use in calves and youngstock (Pardon and others 2012). Public concern to reduce and rationalise veterinary antimicrobial use has markedly increased in the last decade (BelVetSac 2014, MARAN 2015). Veterinary formularies have been constructed which advise sampling, bacterial isolation and antimicrobial susceptibility testing before certain antimicrobial classes can be used (Haneveld 2014, AMCRA 2015).
In human beings and different animal species bronchoalveolar lavage (BAL) is considered a safe and reliable sampling technique to identify causal organisms of pneumonia, because it directly samples the lung lobes (Wilkie and Markham 1979, Pringle and others 1988, Thomas and others 2002). Bronchial fluid can be obtained using an endoscope, enabling selection of the lung lobes to be sampled (Pringle and others 1988, Allen and others 1991). Disadvantages of the endoscopic guided BAL are the need for disinfecting the scope between two patients, the high purchase costs of the equipment and the risk for damage when using endoscopes on farm in cattle. For these reasons endoscopic guided BAL is not routinely applied to sample large groups of calves. Alternatively, with adequate training, BAL can be performed without endoscope using a BAL catheter. Advantages are that BAL catheters are cheap and can be sterilised and reused, making sampling of a representative number of animals in a limited time frame possible. However, there may be some drawbacks. It is unknown whether blind sampling with a BAL catheter does sample the ventrocranial lung parts, where the vast majority of bacterial pneumonias in calves are situated (Allan and others 1985, Allen and others 1991, Dagleish and others …