Oatstraw seed; oat straw is the stem of the cerial grain, oats after they come out in head (start forming seeds).
Go to any animal feed place and buy oats (unhusked animal feed); organic if you prefer, look up oats on the net; agricultural sites, and take a look at the plant and the seed. If you harvest the straw green, leave some to ripen for the seed and then harvest the straw for the ecru variety.
All parts of the plants at all stages of development make excellent chicken feed. Green oat hay is the whole plant, cut while still green and in head, dried in the field and collected into bales. The ripe plants are cut and threshed for the seed, generally for animal feed and seed for the following year, and the straw (what is left after the ripe seed is removed) is used for animal bedding as a rule, or for roughage in animal diets.
It is an ideal animal bedding because it is very absorbant and composts easily.