Free ranging chickens are getting it anyway from what spills under bird feeders. OP is just feeding it as a treat, not their meal. I would never, ever advise raising a chicken on bird feed. They wouldn't survive most likely. I also don't add red pepper flakes but many, many people believe...
I actually ADD flax seed to the grain mix I ferment. Not very much though as it gets mushy. I bought it to add because I read about all of its benefits, of which of course, I couldn't quote you right now and too lazy to google it. :)
Like others said, what you bought should be fine for a...