I know this is a few years old but wanted to bump it up see if anyone has more information to offer, any updates and Ill add a couple of links with more information. I personally have just started both my horses on Chia seeds and I’m getting them at Costco.
https://equinenutritionnerd.com/2015/08/03/feeding-chia-seeds-to-horses/
https://www.savvyhorsewoman.com/2016/01/chia-seeds-for-horses-top-10-benefits.html