redcows.. that is not entirely true.. The liver is a great storehouse of minerals, but that doesn't mean a mineral panel done on blood is worthless.. I did ONE mineral panel on a cow.. the heaviest producer of the herd that had troubles breeding back.. her blood phosphorus, selenium, and copper levels were all rather low.. So I would say because the liver stores minerals, just because the blood levels of (say copper) are within tolerance, doesn't mean the liver stores aren't depleted... however, if the blood levels are low, you can be CERTAIN you have a deficiency
I would HIGHLY recommend a blood panel done on a heavy producing cow a couple months after calving.. that should give you a good idea of what's going on.. mineral levels in the soil can change in 50 miles quite drasticaly (we have a molybdenum mine 10 miles away, and a copper mine 50 miles away, but we're terribly low on copper) A nutritionist isn't going to be of much help without knowing YOUR cows, and the only way he's going to be able to give you sound advice is from a blood test. Butchering a steer and doing a liver analysis on him isn't going to yield you good results because he's not producing milk.
You can start by paying close attention to physiological signs in your cows.. black cows go red with low copper, red cows get a 'netted' look on their hide, and white cows don't show anything at all, though perhaps you'd notice their immune system not working as good as it could.... Selenium is *usually* first seen as weak calves and retained placenta, but for Branguscowgirl it was a paralysis. Phosphorus will usually show as the cows chewing on wood, bones, and rocks. I put a LOT of work into researching mineral deficiencies, and compiled what you may call a brochure.. anyone who wants a copy of it can PM me their email and I'll send them a copy.. I have it on google docs as well but it isn't nicely formatted