Assuming Georgie is otherwise well in herself and is active and eating as normal, has not had any vomiting or diarrhoea, there are a number of things that this could be.
Do you have any idea which end the smell is coming from? This can help to narrow things down. Equally if she is showing extra interest or licking a certain area excessively, this may direct us to the issue.
The first thing to consider would be that the smell is coming from her mouth. An ammonia-rich or fishy smell can be associated with dental disease. Through dental disease is rare in a young dog, some dogs who are teething can develop temporary gum inflammation. Also, any debris or foreign body stuck between teeth can cause a foul-smelling abscess. If she allows you, have a good look in her mouth for any red gums or debris.
Another cause of fishy breath would be a diet change. Any new food or treats with fish as a predominant ingredient?
Most of the time, fishy/urine smells come from the back end.
Anal glands have a particularly fishy smell. Has she been scooting her bum on the floor or looking quickly behind her? A vet will be able to feel her anal glands (which are just inside the anus) to check for an impaction or infection. They may need to be emptied.
A bladder or urine infection is a common cause. This may also be accompanied by symptoms such as excessive drinking, urinating more often or urinating in drips and drops. You may also see urine staining on the fur. If you bring a fresh urine sample to the vet they will be able to check it for infection. Collect the first urine of the day in to a clean pot.
If she is coming into season, there may be a ild odour associated with the discharge, although a fishy odour would not be expected.
You may have already done this, but it is worth bathing her in a mild puppy shampoo to see if this helps. For example, if she has secreted her anal gland contents and they are lingering on the fur, this would help.
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