Notes: In smaller herds, all cattle second or higher lactation must be tested. In herds with fewer than 30 second- and higher-lactation animals, first-lactation animals must also be tested. Sample numbers above have been based on the following assumptions:

• The cattle to be tested are in second or higher lactation.

• For these calculations, ELISA tests was assumed to have 25% sensitivity and fecal cultures was assumed to have 40% sensitivity (These were consensus estimates of the Herd Status Committee of the NJWG, USAHA for sub-clinically infected cows in first or higher lactation, and no changes were made for older populations sampled.)

• For these calculations, 100% test specificity of the ELISA and fecal culture was assumed (given follow-up of all ELISA positives with fecal culture).

• The confidence of detecting infection (at least 1 test-positive cow), if present at a true prevalence of 2%, is 95%.

• Sampling without replacement.