I live in Western PA where the grasses are said to reach "maturity" in 28 days. I currently run 13 head of cattle in two paddocks that are 12.5 and 2.5 acres. I am considering fencing another 4 acres and then rotating the animals thru at 19,3, and 6 days, respectively. I have always heard that you figure 1 acre for every cow/calf pair. With intensive grazing as I plan, how many animals can I work on this arrangement?