Fig. 4.

Correlation between bulk tank milk optical density ratio (ODR) and 10-heifer pooled-milk ODR in grazing herds with a veterinary diagnosis of lungworm (red circles) and zero-grazing herds (green triangle). A) shows ODR values of the two tests. The diagonal hashed line relates to line by which x = y and horizontal line the suggested positivity cut-off for the pooled-heifer test (0.16). B) Bland-Altman plot comparing difference between tests (10-heifer pooled test minus bulk tank) with mean of both tests.