The Shulchan Aruch · Yoreh De'ah
יורה דעה ל״גYoreh De'ah 33
Siman 33 of 402 in Yoreh De'ah — 11 se'ifim
הלכות טריפותUnslaughterable Animals· siman 33
Se’if 1א׳
נִטַּל הַלֶּחִי הַתַּחְתּוֹן, כְּשֵׁרָה, וְהוּא שֶׁיָּכוֹל לִחְיוֹת עַל יְדֵי הַמְרָאָה וְהַלְעָטָה. הַגָּה: וְכֵן עוֹף שֶׁנִּטַּל חַרְטוּמוֹ וְיָכוֹל לִחְיוֹת עַל יְדֵי הַמְרָאָה וְהַלְעָטָה, כָּשֵׁר. (א"ו הָאָרֹךְ כְּלָל נ"ד וְרוֹקֵחַ).
If the lower jaw was removed, it is valid, and this is if [the animal] is able to survive by means of having food stuffed all the way down its throat and having food stuffed partially down its throat. Rema: And so too by a bird whose beak was removed, and it is able to survive by means of having food stuffed all the way down its throat and having food stuffed partially down its throat, it is valid.
Se’if 2ב׳
נִטַּל הַלֶּחִי הָעֶלְיוֹן, לְהַרַמְבַּ"ם טְרֵפָה; וְרָאוּי לָחוּשׁ לִדְבָרָיו.
If the upper jaw was removed, according to the Rambam it invalidates the animal. And it is fitting to be concerned for his words.
Se’if 3ג׳
וֵשֶׁט אוֹ תֻּרְבַּץ הַוֵּשֶׁט שֶׁנִּקַּב לַחֲלָלוֹ, בְּכָל שֶׁהוּא, נְבֵלָה.
The gullet or the entrance to the gullet, that was punctured [until it reached] its [inner] cavity, if [the hole] is any size, it is [considered an] improperly slaughtered animal.
Shulchan Aruch, Yoreh De'ah — Torat Emet 357 edition, via Sefaria — public domain
English: Sefaria Community Translation — CC0