For serious cow protection around the guy anchors and tower of meteorological towers (which were 45 ft TV antenna masts with 1 anemometer and data logger on tower near base)--I've used a special type of barbed wire called "concertina".    It comes in a roll and telescopes out like a slinky.  It can be cut into segments and curled around guy points and towers to keep animals from scratching on anything and toppling tower or damaging something. Use short malleable wire to tie a segment of it together into a circle around the item needing protection.   Undo the tie wire and pull the segment away temporarily for raising and lowering or other access.  

Don't confuse this with "razor ribbon"--a similar type of wire used around prisons--which will literally cut you to bits.  The wire here is merely barbed, but is still nasty to work with--use thick gloves.

If no concertina available,   solid posts can be sunk and regular barbed wire strung--but this is not as flexible for access or raising and lowering.  

Probably one can jury-rig concertina which will act as a deterrent using barbed wire made into a slinky arrangement as above, with a connector embossing tool to connect 4 or so separate barbed-wire strands together like a slinky.  But that will not be as good as the more rigid large-gauge concertina which easily maintains its shape, which most barbed-wire will not do.