FIG 1.

Sampling strategy. A total of 29 barns carrying 37 flocks were sampled, and each icon represents a barn within a farm. A total of 12 flocks were sampled by following four barns longitudinally for three grow-out cycles, and 10 birds per flock and per time point were sampled (left). A total of 25 random flocks of different ages were sampled in a cross-sectional fashion using six birds per flock (right). Each flock sampled came from a geographically distinct farm within a single vertically integrated broiler company.