Chickens and cattle and a fly tub

I am wanting to put my chickens on the cattle pasture as a natural fly predator. However, my cattle have had a Altosid fly tub. How long do I need to wait to put the chickens on the field, once I remove the tub? 1. So they don’t get sick and 2. We eat their eggs. Thanks!

"Sunlight and micro-organisms break down methoprene rapidly in soil, water, and on plants. In soil, about half of the original amount is gone within 10-14 days. In water, it takes 1-28 days for methoprene residue to break down by half, depending on the availability of sunlight. "

The Methoprene will be spread in the manure.
I would wait up to 1 year, considering you will be consuming the eggs.

Howdy!
I did a quick look-up and really have a problem with trying to decide what kind of advice to offer. With a 15-30 day  half-life in most situations, and having a half-life of 18 months in another situation (when process into a briquette), it sounds like useful but nasty stuff.

So,  in normal circumstances, try to keep the chickens out of the paddock for a good 4 months, at a minimum. Maybe 2 or three years at max.  Or resign yourself to possibly being flea and fly free, for a bit.
My only real advice is "watch what the birds do". If the drugs are too much, the chickens won't be interested at all in the manure. Then it's just exposure as the drugs leach into the soil/water systems. If the chickens are happy digging into the manure, then you get to decide what you think your actual risks are based on the information you can find.

I can't say much. I treat my dog for heartworm and fleas, so regularly expose myself to some really strong and nasty medications.
Good luck!