Keep to the High Road

The porthmon (lead drover) constantly needed to scan the country ahead: to spot rustlers and highwaymen, to mark the next brook or the next inn, to gauge whether the inn was full by how well-trodden the grass ahead appeared. 

Or maybe to spot pine trees (see below).

He could also be seen by local farmers who might offer a good price for some of his herd.  If he could sell his stock or buy fresh animals for a good price, he would.

Finally, England used to be a boggier place 200 years ago than it is today, and a beast could easily lose a plate (shoe/ciw) as it pulled its foot out of the mud. So low ground was to be avoided.