The phrase "wheat grain" refers to the small seed found within the wheat plant. It is the part of the wheat plant that is harvested and used to make flour for baking bread and other food products. Full definition
Gluten proteins, which represent about 75 percent of the total protein content of wheat grain, are known to be the primary triggers of the immune response in celiac disease. (sciencedaily.com)
One thing to be wary of with this ingredient is that, though oats are naturally gluten - free, they may be mixed with wheat grains depending on the level of purity. (dogfoodinsider.com)