Does barbed wire harm cattle

No. Barbed wire is the most common type of permanent Fencing to use for cattle. It is designed to poke the animals in the skin so they don't try to go through the fence, but it's also good enough for them to scratch an itch on. Barbed wire seems to be one of the most effective types of fencing wire to use to enclose cattle on pasture than other wire.

However, a piece of barbed wire laying on the ground that is ingested by a cow will hurt her. If that piece of wire punctures the stomach wall she will develop an infection called Hardware Disease. But wire on the fence that stays on the fence, will not hurt cattle.