SEED that is!
The first couple handfuls of Oat Grass has come up from the 5 pound sack of "cat grass seed" I bought off Ebay. It has much better germination rates than the stuff from the pet store as well. I got tired of buying those little packets of cat grass and peat in the pet food aisle every week or two only to get a few sprigs of grass that my cats can mow down in a few minutes. Now I have a gallon size ziplock bag full of those seeds. Should last a year or more, the seed may even expire before I even use it all!
If your critters like eating the grass, the only seller on there who sells the bulk bags of seed by the lb has "good stuff"!