The question was "How Old can a Bull get r done?" and now I notice the operative word was "effectively". Well, I reckon there is a difference in performance and deliverance, so disregard my last post. For some odd, and obviously demented reason, I had recall that was inappropriate for this discussion. Please forgive me, and carry on.
I cannot add to the discussion on bulls because I trade mine out every couple years. But on cows, I have a couple that are pushing 18 to 20 years. I don't know for sure because I bought them out of what was part of my grandads herd, and only have hearsay from other family and neighbor friends to go by. I reckon when I walked in on them after the coon hunt would have been a good time to get all the particulars