Here is a really good informative video about chia and other fat sources: http://www.youtube.com/watch?v=TVGjDTDw1YY&feature=related
According to Tigger (the lady in the video) we should only feed chia from Mexico, Bolivia and Ecuador. We also should be feeding it wet (gel).
Feeding rate is 2-4 TB. per feeding. 1/3 of a cup for metabolic horses.
Here is their website for BioStar EQ - I had never heard of them until someone sent me this video: http://www.biostareq.com/ Lots of interesting stuff on there about feeding whole foods. BTW - they offer a 5 lb. bag for $46. Organic.
I’d love to try chia, but I’ve got to find a source I can afford. I currently feed NutraFlax and go through 40 lbs. in about 5-6 weeks with my 4.