Far from what people imagine, the spirit of an animal does not expire with its death. The spirit of the animal goes down into the earth. And so earth is placed over the animal’s blood which contains its spirit, so sacrifices are something outside and above nature, something other worldly.
...therefore regarding animals that were slaughtered outside [the traveling tent] it is written "it is considered murder [literally blood] as one who spills human blood. Because when it was sanctified as a sacrifice, it rose to the aspect of a human being," as explained above.
In other words, when an animal is sanctified as a sacrifice it rises to the aspect of a human being, so that if it was not afterwards sacrificed properly this is considered as having murdered it. That is why regarding this sin the Law uses a term reserved for murder.
Mind boggling!!
Where into the earth does the spirit go? What happens to it then? Why does the animal need a repair? Perhaps we will have to wait until the redemption to find out.