Expected Progeny Differences (EPD) are best used in comparing one bull (or cow) of the same breed to another. Simply put, if a bull has a birthweight EPD of 5, you can expect his calves to weigh five pounds more at birth than if you breed the same cow to a bull with a BW EPD of 0. If his Weaning Weight EPD is 40, you can expect his calves to weigh 40 more pounds at weaning than if you bred that cow to a bull with a WW EPD of 0. Here's a link to a Angus Association site that has a good explanation on what EPDs mean and how to use them. Good luck...
<A HREF="http://www.angus.org/pubs/bullbuy.htm" TARGET="_blank">http://www.angus.org/pubs/bullbuy.htm</A>