Usually if you put a young bull with an older one it should be fine. They may get into a little tiff at first, but the older bull would easily dominate and get the young bull to behave himself right quick. You will get more problems if you get two bulls that are not familiar with each other of the same size and stature.
Do these guys know each other, any horns, what breed, are your cows preg. Do you need two bulls ???? Pinch the young one or butcher the 4 year old.
You might get away with it or it could be a fight to the death but for 5 females I strongly recommend getting rid of one
I'm only familiar with Jersey bulls, but I wouldn't expect this to end well. Our bulls are dehorned, and I've yet to see a fight to the death, but one of them always ends up lame or bruised and battered. The younger bull starts off minding his manners, but the more patient the older bull is, the sooner the young one starts feeling his . . . oats. In this case, there's almost always a cow in heat--maybe it's different if there's not any action on the horizon.
I routinely see up to 30 - 40 bulls in one pasture after breeding season. The key is to give them plenty of room to separate from each other. They will quickly establish a pecking order, and the biggest bull is usually at the top, but not always. I would guess that your 4 year old will quickly show his dominance, and that will be it. Be sure that the older bull doesn't keep the younger one away from the feed and water, and you will be fine. And---yes, there will be a skirmish, but it will be short lived.
thank you all....If I put the younger bull and his heifer in a feild that has a 20ft "No mans" gap between the older bull and his cows will that be good ??