Which Animals to Assess
To understand how to select an appropriate number of sample animals to use to assess a particular herd, it is important to first understand what the goal of sampling is.
Goal
- To accurately estimate the prevalence of a problem in the herd as a whole.
- To target the population that is at risk for that particular problem.
Auditors seldom have an opportunity to go through the entire facility and look at all pigs so we rely on sampling.
Each audit will have specific instructions on 1) whether or not to sample and 2) how to sample.
In the US, the Common Swine Industry Audit has very detailed instructions on sampling for each age and stage of animal.
Refer specifically to the audit instrument for your instructions. It is also recommended, if possible, to ask for the current animal inventory by phase prior to arrival. This information may chnage before your arrive on the farm, but will still assist with calculating your animal sampling protocols and planning the flow of the audit once you arrive at the site.