Question: Do I put ang or si/sina before a dog name?

Si/Sina ... a name is a proper noun, even though you say "ang aso."

@chappa Yes, you do.

Maraming salamat po ^^

I realized my reply did not answer the question. Yes you use si/sina for names of humans and pets, but if you are not specifying a name, you use the ang marker. There are many more markers you will need depending on the focus, but this answers your specific question. Kinain ko ang aso. = I ate the dog.
Kinain ko si Rover = I ate Rover.

the second reply doesn't sound very good either, surely I fed the dog sounds much better.

@AMBoy Haha! Maybe a better example:
Pinakain ko ang aso na lang o pinakain ko si Rover XD