its hereditary. treated? no. you can assist the calf to nurse or milk them down so that the calf can latch on but once they get big they will always be. the calf will suck them down but next time she calves they will be big again and you will have to assist again (most likely). they will get bigger and bigger, if you dont make sure they get milked they will sometimes get mastitis. other common problems are loss of calves b/c they get discouraged when they cant get the teat in their mouth, and cows tend to step on their larger teats when getting up and thats nasty. the teat tip will slough off...
Ive always heard (and found this to be the case in our herd) that big teats are inherited from the bull. we had an old charolais bull that all of our big teat cases traced back to.