I would just like to comment that if you love animals, you should hate pets. The amount of animal factory farming (killing of animals often more intelligent than your canine) required to nourish a domesticated animal over the course of their lives is gross in all senses of the word gross.
I think another perspective to consider here is how this applies to rescue dogs. I rescued my dog, but from your pov it would’ve been a better idea to euthanize her to spare the lives of all the other animals she would’ve consumed in her lifetime.
Few more things that come to mind:
1. Nature does not reward for smartest, but for the fittest. Which is interesting in itself
2. Argument could be made the same for humans (there are some people that are not worth the life of a farm animal, for example). But also one could say that the summed intellect of all animals that have been killed for consumption for one person in their life time may be net more than that person’s intelligence