Contribution of each term in the models to the average infectivity.
A. Contribution of each term in the models to the average infectivity in each farm, when optimization was done separately on each farm. The first term (α) is infection by free (externally sourced) bacteria. The second term (β) is cow-to-cow infection and the last term (δ) is a constant source. B. Contribution of each term in the model to the average infectivity for each farm when using one set of parameters for all the farms. The main contribution was from the indirect transmission term, and the secondary infectivity is the constant term. There was no contribution from the direct transmission term. The contributions of each term differ among farms, since each farm has a different fraction of infected cows. However, most models yield similar results in the same farm.