Statutes against cruelty to animals, often imposing felony-level penalties, codify society's belief that such cruelty is an intrinsic evil. This is a social affirmation of a strong moral sense in individuals who are not vicious. It is the sense that even though the law can regard an individual's animal as the individual's property, there nevertheless are certain things the individual cannot do to that property. Which means it is property with a difference.
The difference is the capacity for enjoyment and suffering. So why, Scully asks, is cruelty to a puppy appalling and cruelty to livestock by the billions a matter of social indifference? There cannot be any intrinsic difference of worth between a puppy and a pig.
-George F. Will July 18th Newsweek article
"What We Owe What We Eat"