One problem I have often had with bottle calves is that they have a tendency to suck on one another's body parts. Often they will suck their mates in the udder area, even though there is no udder there yet. I've read that this can cause harm to the future udder, although I don't know how true it is. I have always attempted to keep calves that suck on one another separated, hoping they will get over it eventually.
Calves that are raised at their mommy's side never show this kind of behavior for the simple reason that there are four lovely teats hanging down conveniently, twenty-four hours a day; when they feel the urge to suck on something, there they are. The patient mother cow will gladly stand as long as it takes for her baby to get tired, even if the teats have been sucked dry for the time being.
One of my two-month-old calves is a little sucker; his pacifier of choice is Grace's ear. I have been keeping them apart most of the time because of this; when I do finally turn them loose together, the first thing George goes for is that ear. He has a fetish of sorts, and he will not be denied. There are devices I could put on his nose that would keep him from nursing on an udder, but nothing that would prevent his sucking on an ear.
I'm tired of fighting it, and I really want these calves to spend more time together in the larger pen. The only real harm that could come from his behavior is that if he did it when the temperature is zero, Gracie's soaking-wet ear could freeze. I've decided to turn them out together during the day and see if he eventually gets tired of this practice.
When I uploaded this video to Youtube, I noticed a related video that you might find interesting: Click HERE.