It isn't even used for bugs in feed.. it's used and approved as anti caking agent at a rate of up to 2%.
Hi there, hope you are enjoying BYC!
DE, not welcome here EVER.. and it doesn't work in wet environments like inside the intestines.. it does not prevent nor will it have ANY impact on internal parasite load.. studies which SHOW the DE is
ineffective as a worming agent under the agriculture bullet...
https://en.wikipedia.org/wiki/Diatomaceous_earth
Just a fun fact sheet..
http://npic.orst.edu/factsheets/degen.html
Please note that you cannot prevent what you may not have. Some feeds even already have DE on the ingredient list.
DE states
on the bag that it does not work when wet.. like inside the intestines is.
Best way to "prevent" intestinal parasites.. good nutrition, good waste management, not over crowding, don't invite wild birds or animals to your yard by hanging feeders for them.
After all that.. IF your see SYMPTOMS get a fecal float and species load count.. or do them a couple times per year in different seasons and see where YOUR parasite load stands in order to come up with a treatment or prevention schedule that's appropriate to YOUR flock.
Despite seeing yellow frothy poo, muddy bumm and other symptoms many will SWEAR is worms.. a fecal float done by my vet showed NO need treat.. so far in 10+ years of keeping chickens I have YET to need to treat for worms.. at MY location with my weather pattern and my stock density.
Noting I am on the coast where humidity is high ALL the time.. DE is also completely ineffective against external parasites in my location. Adding your general location to your profile can help folks make their best suggestions possible at a glance.
PLEASE.. if you DO choose to use DE
as a worming agent.. get before and after fecal floats and report your results to us.. help find the whole truth instead of perpetuating false senses of security.. and tag me so I can see too.
One final note since you're asking about worms.. the ONLY worms that will EVER be seen in dropping are large round worms and tape worms.. all others will stay inside the intestines and only their microscopic oocysts (eggs) mill pass, never to be seen by the naked eye..
Kinda funny that you call 12 a "small" flock! You MUST be a chicken person.