A mineral/vitamin insufficiency has never been described in horses on a diet of adequate levels of the right seaweeds and forage.
As it is a purely natural product with no industrial additions assume levels akin to that of published Seaweed figures. Published requirements such as the US NF figures show levels being met.
Commercially suggested levels of what the horse needs reflect the extras they may need when only feeding more singular industrially produced minerals and vitamins. We have over the last few years become Paul instead of Saul.
Previously, for more years than most people have been alive, we diligently attended to and tried to balance every last milligram. We have now found that feeding real quality processed algae such as that found in organic EQUINOURISH (it was originally a French idea which, to start with, we were really most dubious of) to horses, as long as everything else is equal, is not only better for them but they perform better and have less problems than horses fed industrially produced minerals and vitamins.
We still consider the use of specific man-mades in recovery and remedial situations but even in such cases it appears that ordinary commercial balancers, (not case specific ones) many we have designed in the past, are of little consequence.
We do however recommend feeding Western Salts and we can add industrial minerals and vitamins to them to make what we call Western Salts TM, so if you are advised of a particular deficiency having calculated the contribution from the grazing or hay we can add it at no great cost.