In artscroll note 17 on 5b2. A chatas .......must be left to die. see Temurah 22b.
Why do you lock it in a room and leave it to die no food and if money throw it into ocean? Hard concept to comprehend?
DSG, New York,U.S.A.
(a) There is a clear logic for why the Chatas is left to die, and its value is disposed of. Once an animal has the Kedushah of a Chatas, it or its value must be used for the Chatas that it was designated for. (Unlike other Korbanos, the Chatas must be designated for a particular sin . It cannot be an generic Chatas, to be used when needed.)
Normally, when we redeem an animal, its value can be used to offer the same type of Korban. In the case of the five Chata'os that die, the sin no longer needs to be atoned for (because the owner died and cannot be atoned for, or because he sacrificed another animal in its stead, etc.). Since the sin cannot be atoned for with the Chatas, nothing can ever be done with it or its value, which is Kadosh. That is why we dispose of it or its value.
(b) Regarding the humanitarian issue, below you will find what Rav Joseph Pearlman responded when another reader asked a question about that in the past.
How do we reconcile the status of a chatas mesa which ostensibly appears quite cruel with the injunction against tzaar baaleh chayim?
Joseph Neustein, M.D., El Paso, Texas USA
Animals exist for the service of mankind and are for food or sacrifice or for other positive function. This includes the performance of Mitzvos and also reasonable experimentation for medical purposes for the benefit of mankind (Rema, Even ha'Ezer 5:14).
Thus, the goat to Azazel of the Avodah on Yom Kipur (Vayikra 1610) was necessary for the sake of Hash-m's commandment, however cruel it might seem to us. Another good example is in the Shulchan Orech, Yoreh Deah 24:8, Rema and Shach (#8), quoting the Mordechai and others, and see also the Pri Megadim in Sifsei Da'as there, regarding plucking the wool or feathers from an animal that interfere with the Shechitah.
It should be noted also that the Noda b'Yehudah (Mahadura Tinyana, YD #10) holds that Tza'ar Ba'alei Chayim, the prohibition against cruelty to animals, has no application where the animal is being put to death. Others, though, disagree.
Hence, there is no problem with Chato'os ha'Meisos, as there is no alternative possibility with sound Halachic reasons as to what to do with the animal. (Since it is being left to starve for the sake of serving a Halachic purpose as mandated by G-d, it is not considered Tza'ar Ba'alei Chayim.)
However, where these considerations do not apply, one is certainly obligated to treat animals
with kindness, as a number of sources in the Gemara and Halachah clearly indicate. Moreover, apart from all of the specific Mitzvos in the Torah (such as lifting the heavy burden off of an animal that has fallen down, the prohibition against muzzling an animal to prevent it from eating while working, letting one's animal rest from work on Shabbos, the prohibition against working two different types of animals together, the requirement to feed one's animals first before eating, and Tza'ar Ba'alei Chayim), there is the general overriding principle of emulating G-d's trait of "v'Rachamav Al Kol Ma'asav," Hash-m "is merciful upon all of His creations."