I try to buildmy fences with 5-6 strands of barbed wire, depending on what I'm trying to keep the cattle in or out of, with the bottom wire 20-21" above the ground, and the top wire ataround 5'. If cattle can stick their head over it or between the wires, they will push through it. You also don't want deer trying to pass between the wires.

The reason I put the lower wire at that height is because most deer (and hogs[:@]) go under the fence. At this height, the fence is not a barrier to wildlife, only cattle. The only thing that won't go under the fence are the larger bucks, and they have no problems jumping a 5' fence.