dog cough and throw up white foam?

Sounds like he just got over excited. It's not uncommon and he should be fine.

My dog used to gag and spit up white foam too. She chewed on things a lot though and only spit up once in awhile. I just assumed she had something stuck in her throat. She was always fine afterwards. Never any problems. You should take her in though if you're worried and if she's doing it so often. Maybe something is stuck in there and she can't get it out. Or at least call the vet and see if they can offer any advice.

he could be over excited, could have eaten some grass but it could be worse and he could have kennel cough which can be serious. if he keeps coughing etc or a wheezy type cough you need to take him to the vet for treatment. a lot would depend on whether he has been vaccinated or not.

My Lab/Shephard does this in the Spring and Fall due to allergies.

P.S. I hope that expensive canned food you're feeding him says COMPLETE and BALACED on the outside label.

My dogs have done that before too! I believe it is just over excitement that causes is.