I ran across this while looking for a vehicle barrier gate for our
farm.
http://www.qcsupply.com/50008-drive-thru-electric-gate-adj-13-19.html
My parents' neighbors had this version:
http://www.grahamindustries.ca/wp-content/uploads/2010/10/CattleGuard.jpg
People always called it a cattle guard. I have no idea if it would work
for other livestock.

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