Does cross breeding, say an Angus NH+ bull on a Hereford cow, solve the problem? 

I am in a much smaller and different system than most of you, but my rule is anything open in the fall at preg check time goes for a trailer ride asap - and before starting hay feeding.  Why keep an open cow at current prices?

5 or 10% open just comes right off the top of your profit.  If it's definitely a bull problem he goes too. But if a bull breeds 95% of the herd it seems to me it's a cow problem not a bull problem, other than nh etc which should never be allowed in the first place. Most bull sale catalogs I have seen list their bulls as xx defect free etc. If someone will not guarantee their bulls as defect free then find another bull supplier.

If you don't cull the opens, maybe she does have a heifer calf next year which you keep, then after 2 years the heifer comes up open and the problem just multiplies.

jmho.

Jim at Dawn