I know someone who had that same "secret" recipe. Her Hackney road pony was always looking good. Make sense. Egg protein is the perfect protein.
Anyway my 2 cents on flax products:
They are a ton out there. They are ground flax, maybe some vitamins and minerals, maybe some prebiotics, maybe some filler. You pay dearly for the convenience of having them grind it for you. They take a product that will run you $.80/# when you buy it from the feed store whole and jack the price up over $5/# if you're not careful. If you have to buy it online and pay for shipping...
... Most of the brown flax is grown in ND and Alberta so it shouldn't be that hard for your feed store to get it in if they don't already carry it. You will feed about 4oz (one tuna fish can) a day. It will complement the MSM nicely. It's good to start the coat additives now as the summer coat is coming in.