About the only way to know what is in a mineral would be to check the feed tag. Hard to tell otherwise. We feed loose mineral with selenium in it. You can try testing the soil or better yet asking neighboring farmers (local dairy farmers would be best to ask in my opinion) about selenium deficiency in their herds.
If you have had white muscle you probably are low in selenium. Just watch the feed tags and get one with selenium in it. My guess is if you bought a mineral with selenium in it you would not have a problem with too much selenium from what you describe...but it is just my opinion and local cattle owners in your area would be a better source of info in this case.
If you have had white muscle you probably are low in selenium. Just watch the feed tags and get one with selenium in it. My guess is if you bought a mineral with selenium in it you would not have a problem with too much selenium from what you describe...but it is just my opinion and local cattle owners in your area would be a better source of info in this case.