The Rambam (Hilkhot Ma’akhalot Assurot 3:11) enumerates six types of neveilah including a puncture in the trachea and a disconnection of the esophagus. Animals with these conditions are considered to be neveilot even while they are alive, so that even if a shehitah is performed on such animals, they remain neveilot, in contrast to other animals with conditions that render them treiphotת which do not become neveilah if slaughtered by a valid shehitah. Many have been perplexed by this statement, unaware of the basis for the Rambam’s ruling.
First, even if shehitah does not prevent an animal with such a condition from becoming a neveilah at death, how is it possible that any animal can become neveilah while alive, as the Tosaphists (Hullin 32a) write, an animal with such a condition is considered, while alive, to be a tereiphah, except that shehitah does not prevent the animal from becoming a neveilah at death. Second, there are many sugyot that contradict the position of the Rambam, e.g., Zevahim 70a, stating that tereiphah is more stringent than neveilah inasmuch as the status of tereiphah can be applied even to an animal that is alive, while the status of neveilah is applicable only to a dead animal. Similarly the Gemara in Hullin (37a) states that a mesuqenet [an animal on the verge of death owing to general weakness or sickness but not a specific defect] is not in the same category as a neveilah, because it is written “כי ימות מן הבהמה” from which it is inferred that an animal becomes a neveilah only at death.
The Lev Aryeh cites that passage to refute the suggestion of the Tevu’ot Shor and the Pleiti that the Rambam admits that, although an animal must actually die before the ritual uncleanliness of neveilah devolves on it, the prohibition of eating neveilah may devolve upon an animal even before death. But the Lev Aryeh observes that, because the verse “כי ימות מן הבהמה” is written concerning the ritual uncleanliness of neveilah, a prohibition on the flesh of a mesuqenet cannot be inferred from this verse. If so, how could many Aharonim have argued that one who cuts off and consumes a piece of flesh from an animal with a punctured esophagus would be liable to be punished both for eating both the flesh of a live animal and the flesh of a neveilah?
But even more astonishing is that none of these Aharonim realized that the Rambam himself explicitly states (Ma’akhalot Assurot 4:1) that to violate the prohibition of eating the flesh of a neveilah, the flesh must be taken from an animal that was already dead.
If one eats a kezayit of the flesh of a dead animal, he is liable to punishment by lashes as it is written: “לא תאכל כל נבלה”. And any animal that was not properly slaughtered is in the category of being dead.
So it is clear that the prohibition of eating neveilah was stated concerning the flesh of a dead animal, which means an animal upon which a valid shehitah was not performed. The Rambam then writes that any animal slaughtered improperly is considered as having died without a shehitah. But the statement that it is in the category of being dead shows that the Rambam was referring to the status of the animal after death. And if the Rambam had meant to say that eating a piece of the flesh cut from an animal before death would violate both the prohibition of eiver min ha-hai and the prohibition of neveilah, the Rambam should have said “it is like a dead animal” (הרי היא כמתה) , or even more clearly it is a neveilah (הרי זו נבלה). But the words “הרי זה מתה” indicate that the Rambam was referring to the flesh taken from an animal after it died.
Earlier iqarim have noted that the Rambam holds the opinion that a small piece of neveilah and a small piece of tereiphah are combined to constitute the minimum requirement of a ke-zayit necessary for punishment to be administered when a prohibited substance is consumed, inasmuch as the Rambam believes that the prohibition of neveilah and the prohibition of tereiphah are really the same prohibition, not two distinct prohibitions. Every tereiphah upon which shehitah is not performed becomes a neveilah upon death, so that when a tereiphah eventually dies without a shehitah, it becomes clear that the animal had been a neveilah even before death. This is an instance of a general principle, because whenever there is a process with a beginning and an end, it becomes clear when the process is concluded that the end state of the process determines the halakhic status at the beginning of the process. Thus, when the process of shehitah begins, the initial cutting of the simanim would render the animal a tereiphah if the process of shehitah were interrupted prematurely. But when the process of shehitah is completed properly, the initial cutting is not viewed as having caused the animal to become a tereiphah, because the successful completion of the shehitah makes it clear that the animal was never a tereiphah. Thus, when an animal becomes a tereiphah, the process of its becoming a neveilah is initiated, so that, unless a proper shehitah is performed on the animal, thereby preventing the otherwise inevitable status of neveilah from devolving upon the animal, the final death of the animal that concludes the process confirms retroactively that the animal was a neveilah already at the moment it became a tereiphah.
But this does not mean that consuming a piece of flesh cut from such an animal while it is still alive would violate the prohibition of neveilah rather than, or in addition to, the prohibition of tereiphah, because the ultimate death of the animal could never retroactively render the piece of flesh cut from the animal while still alive to have been a neveilah at the time it was cut from the animal. In a different context, the Rambam applies the same idea to rule that if a women is divorced on the condition that she perform a specified action, her divorce takes effect retroactively when she fulfills the condition from the moment that she receives the bill of divorce.
Thus, unlike other defects, the puncture of the trachea or a disconnection of the esophagus make it impossible to perform a valid shehitah on animal. Accordingly, the process by which the animal with such a condition will become a neveilah cannot possibly be interrupted, so that it is a certainty that the animal will eventually become a neveilah. The Rambam therefore considers animals with those defects to have the status of a neveilah while they are still alive even though consuming a piece of flesh cut from such animals while they are alive would not violate the prohibition of neveilah.