I've seen some rotting fish guts left on top of some very expensive bonsai at TOJU-en. In Japan It was bound up in a nylon stocking, and from the odor, it was very clear that it was well into the process of decay.
Prepared animal food contains a high percentage of protein and fat, which the trees can't metabolize until it has been decomposed. The bone meal and ash wouldn't hurt. I'm not sure about salts.
You would probably make every pet in the neighborhood happy. If not, you would get a mass of insect larvae after watering a few times, which would be really yucky.
If you still want to try this experiment, go for something that you can carry to the curb rather quickly in case it doesn't work out.
Regards,
Matt