Personally, I can very clearly see that a cow or a dog is concious whereas a plant (if concious at all) is very much further towards unconcious than a human understanding of conciousness. Therefore I opt to reduce the suffering as much as possible.
I would hope if an alien species that was much more concious than we could comprehend were to stumble across earth, they would not cause us suffering and eat us merely because we are not as intelligent as they are.