The primary reason we humans put ourselves on a pedestal and dictate a position of 'authority' over the animals is largely due to our apparent intellectual and technological superiority. But, if our intellect and technology is all the reason to enslave and kill lower-living beings, why not harbor the same attitude towards the disabled and mentally ill, many of whom are lower in intelligence than animals?
The simple answer is that sentience, not intelligence, is the only prerequisite for moral conduct towards others. I recognize that I have no legitimate 'authority' over the animals for the same reason I have no ‘authority’ over the mentally disabled: Both groups are sentient and share the capacity for suffering.
"If it is unjust to cause a human being undeserved pain, then it must also be unjust to cause an innocent animal undeserved pain." - Tom Regan
It is morally abhorrent to violate and cause suffering to any being that has the capacity to be violated. One does not need to possess intellect, or moral agency, to be wronged. Animals may not be moral agents (this is debatable), but they are, most certainly, moral patients; therefore it would be cruel and unjust to cause unnecessary harm and suffering.
It is safe to conclude, then, that the rearing and butchering of farm animals, for something so trivial as momentary taste pleasure, causes immense pain and suffering to innocent animals, and is, therefore, cruel and unjust.
This should be sufficiently obvious to anyone of sound mind and a pure heart.
Thank you for your time and attention.