$EN is an index. EPDs to make it are AVERAGES of potential expectations of calves with a range of lower and higher as expected possibilities. Add a parent with fire and ice mating history, the randomness of genes and you add to your wonderments. Add in constant line crossing and the genes remain more mixed with greater potential differences. A small cow with high milk can have the same $EN as a tall bull with low genetic milk potential. $EN is not the starting point of selection and really tells you anything without knowing background data.