Corrid IS amprolium! and i THINK but won't swear to the fact it should have a 2 week withdrawal before eating eggs? anyone else know about that? i have used and pretty sure the vet said not to eat the eggs for 2 weeks.
Amprolium has no witholding period. If you have the Protozoan in your soil it will only effect the chicks once they are on the ground. How they are packaged or sent has little or no bearing on it.
Amprolium is however a thiamine inhibitor and it starves the cocci to death , unfortunately if used over an extended period of time it can also cause a thiamine deficiency in the host and ultimately lead to wryneck.
