Willy: If you are bent on keeping the Longhorn bull because of sentimentality, want a pasture ornament, to throw small calves if you have real undersized cows or just because of some other intangible reason, well I say more power to you! It's your money that gets spent and you realize and freely admit that keeping and using the Longhorn bull is not motivated primarily by profit motives --- not a darn thing wrong with that.
But IMHO --- IF you are going to buy a few more cows AND definitely keep the LH bull, and you will want to keep a calf or two for your own beef, then by all means buy a couple black Angus cows. In so doing you will (hopefully) increase the carcass quality of your calves ---- unless you really WANT the super lean LH-type carcass. The LH/Angus calves have a good chance of being both black and polled so if you decide not to eat them you'll at least have a little better chance a getting a decent price for them at a sale barn. Consider getting rid of your Heinz 57's and in their place getting black Angus. Arnold Ziffle