I second dividing the supplement between two feedings.
My girl gets a ridiculous amount of powdery supplements so, boy, do I understand this issue.
My favorite "tricks" are: soaking the feed with a little water for about 5 minutes before feeding plus supplement so it all kinda mooshes together, dividing the offending supplement between AM/PM, if splitting it doesn't work - sometimes I found that "nasty" stuff in the PM gets more attention than AM nasty stuff (perhaps after a day of grazing, grain sounds better? I dunno), and then, the piece de resistance is adding a handful of rice bran pellets. As it turns out, my girl is basically addicted to rice bran pellets and will eat ANYTHING with them in it. They also soak really well which is extra great for hiding things.
Also, try changing up the amounts of feed he gets with the supplement. I've found that Lacey is more inclined to eat gross stuff with a smaller amount of grain vs a larger amount. Might you be able to give him half his usual ration in the AM, plus supplement, and give him all the rest of his ration in the PM? If that doesn't work, try putting the nasty stuff in the heftier meal.
ETA- the other thing I do (that you might not be able to do if he's boarded) is wait to give her her hay until she's finished eating her grain. That gives powering through the nasty a little extra motivation, imo, and she's not distracted by the hay (something my girl is famous for being, hahaha).
Fabio - 13 year old Arabian/Lipizzan gelding
Rest peacefully, Lacey.
Last edited by Wallaby; 12-22-2012 at 12:46 PM.