Most small neighborhood type feed stores will be happy to open a bag and sell you 5# or so.
I don't know if you can get TSC or Southern States or whoever to do that though.
I don't suppose that it could hurt - in very small amounts... And I'm SURE that your goats will love it!
I bought a #50 bag of alfalfa cubes for my horse and she acted like I was trying to poison her...
So I tossed a few the the chickens.. they totally ignored the weird, square, green rocks...