AMBoy Jan 10 2021, 6:17am CST ~ 2 weeks, 3 days ago.
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.