I just submitted a stool sample to a lab. Do so every few years as a regular screening. Having just done so I was out walking the dog. Couldn’t help but wonder what I might have heard back from my doctor had I submitted a sample from my dog instead of from me. Would they have known it was from a non-human source? If they were just testing for blood in the stool, and assuming there wasn’t any, would they have even noticed?
If it was just a fecal occult blood test, they wouldn’t know your stool from your dog’s.
Frankly, even if was a study for ova & parasites and enteric pathogens, they wouldn’t know either, unless the sample came back positive for parasities and enteric pathogens that are mainly found only in canines. And since you’re not a canine, they probably wouldn’t even check for canine-specific pathogens and parasites. Even if they did, they might assume you just had a rather closer than usual relationship with your pet. 
“We recommend the patient have a deworming, and chew their tennis balls more thoroughly.”
Old Joke:
This guy has to submit a piss sample to a prospective employer for drug testing. So for fun, he collex from his mother, wife, dog, & daughter, then mixes them together. The employer writes after a few days:
‘Dear Sir: We here at BigCorp regret to inform you that we must decide not to hire you based on the results of your urinalysis. Good luck in your search’.
P.S. We wish you a full recovery from your Alzheimer’s Disease and syphillis, advise you to get shots for your rabies, and congratulate you on your pregnancy’. 