Foreign bodies can do one of two things in a dog: either stick to food and get out of the body (through feces) or get stuck to the intestinal wall, and require surgery.
If this just happened, take your dog to the veterinary emergency asap, and have them work on it. Sometimes they can grab the item with a endoscope while it is still in the stomach. Once it digests to the intestines, you either wait, or get surgery. (Then it is a 50/50 shot that it will come out.)
if a dog eats ants its perfectly fine dogs eat everything
the dog eats poo
Poop
Not much unless he eats too much.
The duck will get sick
you should call a vet
He won't digest it and it may make it sick.
it is an overdose, it can give your dog an infection internaly, dont do it
Nothing. They are harmless.
you have to rush it to the closest hospital or vet
if he/she doesnt have any health problems, nothing should happen.
I would call poison control and your local vet.