Who originally developed the open rage system of raising livestock?

It is not known who originally developed the open-range system of raising livestock. However, it has been around for much longer than Mexico has been around, probably ever since cattle where made into livestock. Much of the people thousands of years ago during or even before Biblical times where nomads, and this is most likely when open-ranging livestock have started. It was not to mimic the wild herbivores that moved around every year, but rather because it was a necessity since grasses were "always greener on the other side." Ancient tribes in Africa still use this system to graze their cattle.

This sort of system was brought over by the Spaniards when they conquered and created Mexico. Europeans who began cattle ranching adopted this practice from the Mexicans. But the Mexicans were not the ones who started this practice.