Murder is wrong, and I find it cowardly for any person to kill a baby that can't even say anything or defend for himself.
Animals differ from humans. Most domestic animals that are severely injured are euthanize. Some can be saved, but plenty of them do not have a great chance of surviving. Animals do not have morals like human beings. Animals are vicious, killers, immodest, and wild. So to euthanize an animal would not result in a crime being made, not unless the animal was perfectly fine, or if the animal belonged to someone and was euthanize without the owner's consent.

It would still be interfering with the creation of a human being. Humans are of more value than any animal. To interfere with the life of human being, would be attempted murder, and to kill the human is murder. There are consequences for those actions.