The white salt block you are referring to is just as you say—white salt. When you feed white salt, plus another macro or trace mineral supplement, those mineral packages usually provide salt also. The reason the intake of your “red” mineral block is low is because the salt it includes is both an intake enhancer and intake limiter. In fact, mineral supplements designed to provide trace minerals but not macrominerals usually are more than 95 percent salt. If you feed white salt in the same pasture as your “red” mineral, the cattle are less enticed by its salt because they are more likely to get salt from the white block. It is common for intake of the mineral to be well below the desired level in this type of situation. It is best to feed salt-limited mineral supplements alone so that the cattle do not have any other potential supplemental salt in the pasture.