i have four horses and only one will eat flax! the mare eats a cup of flax a day but it took a few years of small ammounts of flax on and off and eventually miss picky has decided it is actually food. one gelding will not eat it at all and the other two geldings will eat some of it but not finish it and they are piggies. so i finally give up and after the mare finishes this bag im not buying it anymore. i just wanted shinier horses haha. oh and one of my goats loves it, very shiny goat LOL
i know lots of people who feed flax and all their horses eat it, but i guess i just lucked into picky horses!
if you want him to be shiny canola oil or BOSS should work. but if you are just looking to increase omega 3s i think they would be pointless since they are so high in omega 6s . fish oil might be worth a try, or actually what about flax oil? could you possibly sryinge it into his mouth each day if he doesnt like it on his feed?