Subsampling Age Classes |
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Some measures are only scored in particular age classes due to the underlying causes and consequences associated with them. It would be ideal to score every animal on the farm. However, the ideal becomes impractical on large herds, unless we endeavored to spend several days on a farm. Using a targeted sampling method, we can score a subset of animals to generate a prevalence estimate. We determine the subset to sample based on the risk for each concern.
Groups to Score
In the table below of age class-specific criteria, ideal samples should be taken if time and the housing system allows; minimum sampling is required regardless of time taken.
When calculating farm prevalence for each measure and life-stage group, use the total number of animals of that group observed as the denominator.
When calculating farm prevalence for each measure and life-stage group, use the total number of animals of that group observed as the denominator.
Additional measures not on this list are scored in the same pens that you assess hygiene in: water cleanliness and air quality.
Determining Sample Group
On farms with 100 or fewer animals in a life-stage (milk-fed calves, heifers, or lactating cows), all the animals in that life-stage will be scored. On farms where there are more than 100 animals in a life-stage, we will apply a select group sampling approach.
Using the sample size calculator, round the group number UP to the nearest value in the table.
Examples
Here are some examples about how to calculate sample sizes: Farm A has fewer than 100 animals per life-stage while Farm B has over 100 animals per life-stage. For more information on "Everywhere" measures, review this page.
