I've been around calving heifers all my life. Most of the heifers we've calved have been identified by sire and mother. I can sum up the majority of the mothering in one word. GENETICS!!!! You will occasionally get a dumb heifer from a sire or dam that normally doesn't have these issues, but if you know where the ancestry of all of them came from, you will usually see patterns develop. It's hard to predict beforehand as some sire's will throw daughters that are too aggressive, and you can use a son and they won't be the same. We had two flush brothers that we used for years, and the temperment of those two bulls daughters was totally different. The one's were so gentle that you would have wished they were a bit more aggressive cleaning their calf off, and the other one's daughters would sometimes beat their calf around a while after they calved. The strange thing was, once they became three year old's they chilled out a bit and were usually perfect mother's after that. So trying to predict which one's will do it beforehand is hard to do, but their are certain bloodlines we've used that sure have a higher percentage of it occuring than the rest of the heifers.