After being on this site a while, I have decided that minerals are more important than what some make them out to be from my area. I have thrown the blocks away and went to loose mineral. I have beef heifers and am working toward a cow/calf operation. I recently stopped by the feed store and he sold me what he calls a "spring mineral" with magnesium. He also said the "fly mineral" was good for fly control. Can I keep one or both of these out all year? Is there a basic mineral that people keep out all year, or does it change with the seasons? Do the cows need something different when with calf?