Go to your local Farm & Fleet or Big R store and get a small solar electric fence charger and some of the 3 ft. tall round stakes for electric fencing.[1 for every 10 or 12 ft. of fence]and insulaters and a roll of wire. A single wire is all you need to keep the cattle out. The nice thing about this is you can reuse it. Just remember that good pasture makes good fences. If there is grass for the cows to eat they should stay out of your plot.
I use this for keeping horses off areas I reseed in my horse pasture. Good luck.