If folks are insistent on feeding BOSS, be sure you do NOT buy black oil sunflower seeds that have "bird koting" on them. It will say on the bag if it does.
Yes BOSS is very high in Omega-6 which aggravates inflammation. One of my horses is insulin resistant and it really exploded his arthritis issues, so BOSS is out of the question for him.
I prefer to feed 1/2 cup daily of Omega-3 Horseshine that has the appropriate ratio of Omega-3' to 6's. It has worked miracles on the I-R horse's hooves --- they are stronger now than they've ever been. He is now barefoot and can go down the road without ouching for the first time in his life unless he was wearing shoes.