I use it on all my show horses, regardless of color. I get it at the feed store in a huge sack and grind it with a cheap $5 coffee grinder. Once ground, it will not keep as long as whole, so if you grind it all at once, freeze all but a large coffee can that you are currently using. It also helps horses to shed out in the spring.
For the amount, my baseline is a heaping tablespoon 1x a day, more or less depending on the size of the horse. It doesn't take "a lot" to make a difference.
Here's my silver dapple mare that I had on it. See how shiny she is? She has no "spray on shine" on her and was clipped the night before this picture was taken. Not exercised or anything, either. I took her to a show only to keep her yearling daughter calm / unstressed and this mare won her class and went Grand Champion mare (not too bad for a 2x broodmare who only came along for companionship!).
This is her daughter (silver buckskin):
And see how shiny too it made my silver bay boy:
The flax seed is the only supplement my horses get and all these ones just had a basic clip and bath. These pictures were taken as we unloaded them at home following our state club's summer show.
