They just do it. Some breeds - Jerseys, in particular - are very 'oral' - they explore EVERYTHING with their tongues.

Horses do, too. i unloaded feed from my almost new pickup one day--and while i was unloading, and not paying attention, one mare left teeth marks all along the hood!!

Im surprised they didnt think it was a new girl in town..get it?probably tasted salty.

I agree w/ Jerseys being a bit "oral". We've had Jersey heifers that have a wierd thing w/ their tongue and roll it constantly.. quite annoying. Jersey calves are notorious for grabbing hold of your clothes w/ their slimy little mouths, also.
When I worked for the soil and WAter Conservation District, we were in a pasture w/ Jerseys (my cousin's actually), and had the truck parked in the pasture. There was a heifer that had a ring in her nose b/c she was still sucking off everyone, and she scratched the hell out of the truck w/ the ring. Our manager wasn't very pleased.

They will also pull the wires out of anything left in the pasture with them. Lighting harnesses on trailers are a favorite snack. Cows are very curious creatures and a lot smarter than people give them credit for.

Sarah

Thanks so much everyone! The question had been bothering me for several years, and I'm glad to know the answer!
Kay

I raise beef cattle - mostly black angus , limousines and red angus . They are not nearly as oral as Jerseys but are tremendously curious animals . They will investigate anything out of the ordinary especially vehicles . They remind me of very friendly dogs . Ain't they wonderful ??