Electric fence detail

I've found that a two-strand electric fence is required instead of my one strand, when I've got both pigs and cows in the same pasture. The basic rule is that each strand has got to be nose high for the target animal. So here I've got a high strand that is actually aimed at containing the cattle, and a low strand that is aimed at the sheep or pigs. The sheep will jump over a low strand, or go under a high strand, so two strands are necessary for them. For the cows I can get by with a single high strand, with the pigs, a single low strand.