55. When we packed our food we used food-grade diatomaceous earth for the grains. All grain already has the eggs of insects in it - it's just the natural way. When they hatch out the diatomaceous earth either smothers them because the particles are so tiny or if the larvae is bigger or soft-skinned it dries them up.
I bake my own bread and grind my own flour. In some of the jars where we didn't use diatomaceous there is an occasional weevil and I grind it up - if folks eat animals then a bug or two shouldn't be a problem.
Diatomaceous earth is full of minerals and is a safe, non-toxic way to treat your food. You don't want to breathe it because the particles are so tiny but then, you don't want to inhale flour, either. It's real cheap, too.
We use 1/4 cup for a 5-gallon bucket of grain. We half-fill the bucket, sprinkle 1/2 the dust on, put the lid on, roll the bucket all around, take the lid off, fill the bucket with more grain to the top, add the rest of the dust, roll it around and you're done. You can do it in smaller batches, too. In gallon jars and then pour it into the bucket.
An added step would be to re-open and add a small piece of dry ice to the top. (I like to put it on a piece of broken pottery to keep it from "burning" the grain.) Let the lid rest on top while the dry ice sublimates into gaseous carbon dioxide and displaces bug-breathable air. Then seal tightly.
ALSO: ..I suggest sealing your bags, boxes etc. to keep from getting damp, then freezing them for 3 days..it kills the eggs. I have done this with everything I buy..it works. I have used rice, flour, etc. that is months old (re-stocking as I use). I'm sure it will work for animal feed as well.
You can also drop a couple of Bay leaves in since most bugs hate. Bay leaves are good to use in almost any food storage situation
Another good storage trick for grains and legumes is to use oxygen absorber packs that can be purchased wherever food storage supplies are sold. No oxygen = no living things, and no oxidation of the contents or the container.
To avoid 6 legged critters, vacuum seal your food (see Tilia Foodsaver) and store in 5 gallon plastic buckets with the snap on lids. Or, store food directly in the 5 gallon buckets and pay to have the buckets nitrogen injected. Costs a couple of bucks a bucket. Either of these methods will kill existing critters and prevent future contamination.
Second to vacuum sealing, you can use zip-lock bags. Fill the bag, lower it into a sink full of water until the water is just to the zip- lock. Seal the bag. Remove and dry the bag off. The water pressure pushes a lot of the extraneous gases (air) out of the bag.
Rats can, but won't gnaw into the 5 gallon buckets unless they have a reason to, like the odor of of something yummy on the other side. Properly sealed, a 5 gallon buckets should be odorless.
Rats require 3 things to survive, food, water and shelter. Remove any one of these three things and the rat population disappears.
I have used boric acid effectively for years to keep away roaches, along with Roach Prufe. The last place I was in had ants before I brought in food. One place I had and didn't prepare very many meals, had neither roaches nor ants, but I brought in weevils from the store, and they ate everything resembling a carbohydrate.