I sympathize with your view, but let me clarify. In one sense, every and all legal harm is associated with loss or destruction of property. In this sense, even we are property. Killing us would equate to destroying the property right we have in ourselves. If "property" is to be treated so robustly under the law, then it's no surprise and horribly uninteresting that animals should also be considered property.
The question isn't really whether animals should be considered property. Rather, the question should be how the law should remedy destruction or loss of an animal. This is why I referred to "property law." In property law, we are usually entitled to monetary compensation for the loss or destruction of property. For example, say we bought a ladder for $50, then let our neighbor borrow it, who subsequently breaks it, and whom we subsequently sue. Usually, we are entitled mostly to the fair market value of the ladder or the cost of fixing the ladder, whichever is less. And that's it. We're not entitled to pain and suffering due to its destruction, nor punitive damages, nor is our neighbor subject to fines or imprisonment. Property damages just don't work that way.
If you think someone should be entitled to pain and suffering damages from, punitive damages from, or criminal sanctions against someone who destroys or loses an animal, then you should probably look to criminal law and tort law, and not property law, for your solution.
(Edited by Jordan on 11/02, 1:27pm)