Why does my dogs breath smell like fish?

It smells really gross. This just started 2 days ago. He is a 5 month old puppy. We brush his teeth and give him greenies dental chews. Do you think its the food he eats? We switched it about 2 weeks ago its excellent food (great life buffalo) but my other dog eats it as well and her breath doesn't stink. Any ideas what could be causing this? What caj I do to cure this?

Often, puppies develop pretty unpleasant breath when they are teething. I haven't usually thought of it as smelling like fish... usually it seems more like a coppery and vaguely "off" smell. My first guess is that your pup has a couple of molars coming out...A large fresh raw beef knuckle or femur bone to gnaw on will help with the teething and will do a MUCH better job of keeping dogs' teeth clean and their mouths healthy than Greenies will. Raw bones are for outside or in the crate or babygated in the kitchen... you do NOT want them dragged around the house!

He likes to secretly eat the bitches out! Haha. I know bad joke. But seriously...fishy bad breath is quite normal in puppies caused by them teething. Check her teeth for where adult teeth may be coming in or for redness and swelling of gum. If all looks okay and he is eating okay you are probably fine. If you have a hard time checking or arent sure have your vet look. Puppies usually stop teething around 6-8 months. Make sure you also check that he isnt eating feces. Even just cleaning his hind quarters can cause bad breath especially if he has some kind of intestinal parasite. If he hasnt been vaccinated against worms Id suggest you check to make sure he doesnt have any. Chances are if his poop looks normal he doesnt but ask a vet to be sure and get him vaccinated. My personal opinion, its just thenormal bad puppy breath from teething and you just need to wait until he grows out of it. Give him ice to chew, it will help him teeth faster by loosening his puppy teeth and allowing his adult teeth to grow, as well as sooth his gums. If he doesnt want to chew it try adding something good to it like meat shavings. OR other trick is to take and old rag or tshirt and soak it in water adn freeze that and give him that to chew on. Good luck with your pup.