I was wondering myself how you would know about silica content in dog food.
From the Whole Dog Journal
Other foods that are high in silica, and which should be avoided, include the hulls of wheat, oats, and rice (hulls are found in whole grains); sugar beets; sugar cane pulp; seafood; potatoes and other root vegetables; onions (which shouldn’t be fed to dogs, anyway); bell peppers; asparagus; cabbage; carrots; apples; oranges; cherries; nuts and seeds; grains; soybeans; and the herbs alfalfa, horsetail, comfrey, dandelion, and nettles. Bentonite clay, a mineral supplement, is also high in silicates.
Dogs who drink water from sources containing sand may develop silica uroliths, so water that contains silica (a primary mineral in sand) should be avoided. In hard-water areas, distilled water is recommended for dogs who form silica stones. Silica stones have also been associated with pica, an eating disorder that causes dogs to eat dirt, rocks, and other non-food items.
So not just grains, but some veggies and fruits and seafood. So my Fromm's Salmon Tunalinni is probably not a good one for you. Not sure if they might have something that would be as they have a wide variety of foods.
Gina Pizzo