[header] How to cook or boil whole grains for horses [title] Decide on the type of grain. [step] There are many grains today, and only a handful can be fed to horses, these include barley and oats. There are other grains available to feed, but precautions need to be taken during the boiling and feeding. 
Linseed needs special care as if it is not boiled correctly causes a build up of acid, and also the toxins (which you boil out of them) don't get removed and get into the horses body. Wheat should also not be fed at any time.