Gday there, I'm not sure where you're located, but we send all our hay, grain, silage feed tests to NSW DPI at Wagga. Pretty reasonably priced, a nice report comes back and they're pretty quick. They'll give you sampling bags with all the notes on how to do it, and the kit comes with a free postage paid bag to send it back in. Really simple and easy.
hope that helps
Andrew at Jerilderie