very little, a salt mineral mix with sotbean hulls [20%] near water sorce with Mag. in spring w/o in summer. self limiting, aprox 1# per head per day. They don't need much if you fertilize your pastures...I don't sell fertilizer but i do endorse it.
I've been feeding about 2.5 lbs per day of rice bran and using a mineral/salt block (brown). It seems to stretch my forage a lot further, but I don't know if I'm over doing it. I'm just the opposite of most ranchers. I have limited summer forage, but have ample winter forage (oats/wheat). What kind of loose minerals do you use?
My experience is that the minerals you need to feed varies by different locations. Different soils and forage lack different natural minerals that you therefore need to provide for optimum performance. I'm sure there are some general mineral programs out there that may have a blanket type effect covering a wide variety of needs.
Anyway, we use Moorman's Opticor 646 mineral. It has what we need in our area and takes weather better than most. I know that RFDTV has been airing a program on Cargill's mineral supplementation program and it has been interesting to watch. They promote that you need different mineral blends at different times of year. Makes sense to me.