Thousands, often too many to count. One ranch would have to drive over 500 cattle to the railroad station to be sent to slaughter.
A cattle drive had a variable number of cattle depending on how many needed to be moved. It could be 50 or hundreds.
They become feral or join another local herd or die.
one
There was about 3 to 20 cowboys in a cattle drive. Depending on how much cattle there was varied on the amount of cowboys.