Figure 1.

Seasonality in ELISA optical density. Bulk tank milk optical density of Mycobacterium avium subsp. paratuberculosis ELISA by date of sampling. Solid blue line fitted from cosine seasonality variable with all other variables set to baseline. Herds with seasonal calving practices are red dots. Open circles represent farms that do not graze their cattle. Red open circles are seasonal calving farms that do not graze. Solid dots represent all other farms included in final multivariate model.