When we were trying to figure out all the calves on those cows he brought home from pasture for the preg check... the calves had been tagged but none of the cows were... we tagged the cows as they went through the chute and then about 2 hours later, turned out one calf at a time and watched to see who they went to and SUCKED.... Took about 2 hours or more to do it one by one... we had an idea of a couple, but some were really hard... because they would go to a cow, but because they were not little babies, it took awhile before they actually went on and sucked... We also had sorted the cows into a couple groups as to where they were going to get moved to.... but got them matched... Much easier to do it with littler ones... they go to momma to get a drink as a "sense of security" thing. and the cow will mother up on a little calf quicker.