The nose ring usually works well. I usually put a good sized ring in as this prevents the animal from grabbing the teat with its mouth, yet allows it to graze and eat normally. I have found that this usually works but the chain hanging from the ring can be used in severe cases.
A few years ago, I had a 4 year old cow who had calved and I noticed that her calf was really getting thin and not doing well. It didn't seem sick and it seemed to be nursing often, and the cow milked well. The following day, the calf was even thinner and seemed to be bawling all the time when it wasn't trying to suck it's mother. It kinda had me stumped as the calf had no signs of being sick. Then as I was feeding the cows I figured out what was going on. The cow would lie down and suck herself dry. Talk about the ultimate in recycling!! The poor calf was not getting any milk as the mother cow could reach around far enough to drain all four quarters. She had a ring in her nose faster than chain lightning, and within a day, the calf looked much better. I left the ring in her nose until the calf was weaned and then removed it. I had that cow in our herd for many years and she never did this again.