Animal Health & Welfare

Electronic identification of individuals in the Scottish sheep population

EU regulations introduced after the foot and mouth outbreak in 2001 resulted in the introduction of electronic tagging of sheep in Scotland in order that movements of individuals can be traced should another infectious disease outbreak occur. Batches of sheep pass through electronic scanners at critical control points (CCPs), mostly marts or abattoirs, and the individual identifiers on their tags are read and the data uploaded to a central data base (ScotEID), together with the batch size, date and holding numbers for their departure point and destination. Tags can be lost, or degrade so that scanners fail to read them, and there are increased difficulties in reading tags from large batches of sheep.

BioSS has been collaborating with SAOS Ltd. since 2009 to analyse data on read rates, using generalised linear mixed models (GLMMs) to investigate issues including effects of batch size, scanner type, type of CCP, and age and type of tag. The mean batch read rate in 2011 was 94.9%, and it is now widely accepted that 100% read rates will not be consistently achieved. Since sheep tend to be moved in batches, it has been suggested that 100% read rates are not actually necessary for effective tracing. We have simulated the contact tracing process required in the event of a disease outbreak, and these simulations are allowing us to explore the impact of read rates on traceability.

sheep passing through a scanner Sheep passing through a fixed electronic scanner at St Boswells market in Scotland. Photo provided by SAOS Ltd.

modelled percentage of sheep during 2011 Modelled percentage of sheep read during 2011 as a function of batch size, indicating the differential performance between fixed and handheld tag scanners ar marts and abattoirs

Further details from: Sarah Brocklehurst and Stephen Catterall

Article date 2013

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