we weaned a set on Saturday...now these were my brothers cattle so they are bucking stock not show cattle...I typically leave the buckin bred calves on until they are at least 7 months, but some of the cows in this group we bought at a sherrif's auction and were in pretty bad shape when we got them, they calved and have improved, but with our heat and dryness just were not bouncing back...all the calves were eating feed so I made the decision to go ahead and wean them to try and pull some stress off the cows...the older calves that were out of cows we already had were January and February calves, but some of the calves off the new cows were as young as late April(so only 3 months old)
For show type cattle I tend to play it by ear...I will pull some early and push them on feed if I think they need it, but I still say 5-6 months is a good general rule of thumb for me