posted 7 years ago
A few thoughts:
I don't really see the point in separating him out now. I'd leave him with the cows to make your life much simpler. You presumably have no young heifers you want to avoid being bred, so I don't know what damage he might do. Leave him in, on the other hand, and when the cows come back into heat (say, 30 to 90 days or so), there he'll be, ready to breed them back.
Don't underestimate a horny bull's ability to get to the cows when his services are needed anyway. And being a herd animal, he's not going to want to be alone anyway, even when they're not in heat. That's just that much more incentive for him to disregard your plans of separation.
Putting him 15 days behind your cows will screw up your grass regrowth, yes. It shouldn't be regrazed that soon. For that matter, your 3-day paddocks most likely ain't; grass growth isn't constant. It's better than continuous grazing, sure, but you can do much better with just a little more effort.
Selling him is certainly an option, but you'll need to get another pretty soon. On the one hand, it's kind of a waste to keep a bull for only four cows (wouldn't you rather have an extra cow and calf for the space usage, and just hire a bull for a few short months each year?). On the other hand, dealing with moving bulls in and out can be a pain, and there's a certain likelihood that you hire a dud, or can't get one when you need him, or can't get the breed you want, or just can't get a bull you'd want to put your cows to.
I'd say if you opt to keep him, which is entirely your choice, you're just creating problems for yourself if you try separating him. Unless you have good reason to believe he'd harm the new calves for some reason, I just can't see why you'd want to separate him now.