Quite often you see people use canine and feline as nouns when they are talking about dogs and cats. It’s usually in long sentence with big words in it like this:
“Neural mechanisms of paroxysmal atrial fibrillation and paroxysmal atrial tachycardia in ambulatory canines”
“The scientific foundation and efficacy of the use of canines and chemical detectors for explosives”
It would be all very well if they were talking about teeth. But they are not, they are talking about dogs. They should just say dog. By using the word canine instead, they sound pompous and bombastic. It’s as if they think it makes their work sound more important/scientific/credible. Dog is an ordinary word but it is not slang. It is clear and simple. It is fine to use it, even in academic writing.
So the noun should be dog, but canine is correct when you need an adjective.
“Identification of a common risk haplotype for canine idiopathic epilepsy in the ADAM23 gene.”
“Canine ehrlichiosis: prevalence and epidemiology in northeast Brazil.”
The same goes for cat and feline.