Flax
Flax has a slightly better omega 3 profile than chia seeds, and can be used for the same benefits. Our flax is sourced from the best on the market we have found: Turtle Mountain Flax. They make cold-milled flax with a stable shelf life of up to two years, and I have eaten it myself as it is human grade. My horse Daisy is on their cold-milled flax daily and eats it readily!
https://www.turtlemountainflax.com/
https://madbarn.com/flaxseed-for-horses/
Chia
Chia seeds have an excellent omega 6 to omega 3 ratio with a great fatty acid profile and fiber content. They are also low in starch and sugar.
https://thehorse.com/113167/chia-or-flax-which-is-better-for-my-horse/
https://madbarn.com/feeds/chia-seeds/
Pumpkin Seeds
Pumpkin seeds are a good source of fat and fiber and add a bit of texture to some of our porridges. They are shelled, so only the inside kernel is what we use. Orange pie pumpkins are safe for horses to eat.
https://thehorse.com/113373/can-horses-eat-pumpkin/