I agree w/ what others have said.
Is the poo overly light colored or voluminous? Or gray-ish? That could be a "fatty stool", and a vet should see it.
Either way though, I'd want my vet to see the stool, just to be sure. Like Nancy mentioned, this could just be undigested food but it'd be good to have it looked at.
Also, are these areas more "fatty" or more like mucus? Btw, if there is mucus at the *end* of a poo, this may just be the anal glands emptying. If they are emptying too often though...that may also warrant considering a diet change
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