Castration & Sterilization to humans and animals:
Male humans/animals: It is [Biblically] forbidden to destroy [i.e. castrate] the reproductive organs of any male creature, whether human, animal, bird [or even fish]. This prohibition applies whether the species is Kosher or impure. This prohibition applies whether in Israel or the Diaspora. One who transgresses this prohibition is liable for the penalty of lashes. [This prohibition applies both to the person performing the castration and to a person who allows someone to castrate him.]
Female humans/animals: It is [Rabbinically] forbidden to destroy the reproductive organs of a female creature, whether human or other creature, although one who does so is exempt from lashes.
Castrating additional reproductive limbs: If one of the reproductive organs were already destroyed, it nevertheless remains [Biblically] forbidden to further destroy the organs. One who does so is liable for lashes. This applies to any [male] creature, whether human, animal, bird [or fish]. For example; If one person castrated the penis and a second person castrated the testis. Or, if one person detached the testis and another person cut the nerves of the testis. Or if one person crushed the penis, and a second person detached it and another person cut it off, each of these people receive lashes, even though the latter person castrated and already castrated person.
It is forbidden to castrate the reproductive organs of any creature, whether human, animal, bird or fish, whether male or female. One who castrates a male creature is Biblically liable for lashes. It is forbidden to further castrate even an already castrated creature.
Is a gentile prohibited from castrating a human/animal as part of the Noahide laws?
This matter is disputed in the Talmud and Poskim. Some Poskim rule that gentiles are not prohibited against castrating. Other Poskim rule that gentiles are prohibited against castrating. Practically, one is to be stringent like the latter opinion. [The practical ramification of this matter is a) Can one sell an animal to a gentile if one knows he will castrate it [this matter will be explained in a further Halacha], and b) What should one instruct gentiles to do, if they desire to keep the seven Noahide laws.]
Q&A on medical procedures
May a man have a vasectomy?
As stated above, it is Biblically forbidden for a man to have a vasectomy performed on him or to perform a vasectomy onto another human being or creature.
If one’s wife will be in danger if she gets pregnant: There is no allowance to do so even if it is medically forbidden for his wife to become pregnant. Rather, other contraceptive measures must be implemented in such a case.
May a woman have a Hysterectomy [her womb removed]?
It is permitted for a woman to have a hysterectomy performed if she is in a case of danger. Furthermore, some Poskim rule it may even be performed to prevent great pain, even if she is not in danger.
Male: Chemical sterilization, such as through drinking a sterilizing liquid, is [Biblically] forbidden to be done to any [male] human or animal. Nonetheless, if one does so, it does not carry the penalty lashes. [This prohibition applies even if the man already fulfilled the Mitzvah of Peru Urevu, and even if he is already sterile due to other reasons. However, some Poskim rule it is permitted for one who fulfilled the Mitzvah of Peru Urevu to drink a chemical sterilization for the sake of removing his lust and, so he be able to learn Torah without disturbances. This prohibition applies even if the intent of the liquid is for medicinal purposes, and one has no intent to make himself sterile, and it is even against his will. Nevertheless, in a case of a potentially lethal illness, it is permitted to drink it for medicinal purposes, even if it will cause sterilization. Likewise, a male animal who is carrying a deadly disease whose cure requires chemical sterilization, some Poskim rule it is permitted to do so. Other Poskim however rule one may only do so through a gentile. A male who transgressed and performed chemical sterilization to himself, may nonetheless marry a Jewish woman, and does not have the status of a “Kerus Shafcha”.]
Female human: A woman may drink sterilizing chemicals in order to prevent her from giving birth. [This applies even if there is no justifiable reason for her to do so, and she does not experience pain in childbirth. Other Poskim however rule this only applies if the woman has pain in child birth [or to prevent spiritually unhealthy children from being born]. It makes no difference whether a woman drinks the chemical herself or is fed it by others. In all cases, a married woman must ask permission from her husband before doing so. If the husband refuses to grant her permission, she may only do so, under the direction of a Rav, to prevent great pain. Alternatively, she is to be granted a Get from her husband.]
Such as inciting dog to attack genitals, or placing person in very cold temperature-Is forbidden but no lashes
Preventing mating of animals:
Asking gentile to castrate an animal:
Selling animals to gentile/Tzaar Ballei Chayim:
Selling: May sell to gentile despite knowledge that he will castrate the animal. However, some forbid this if the buyer himself will for certain castrate the animal.
Inflicting pain to animals: Is allowed when done for a need.
May one have his pet sterilized?
Male pet: It is forbidden to sterilize a male pet through the removal of his organs, or through chemical sterilization. This applies whether one is doing it himself or is having someone do it for him.
Female pet: Some Poskim rule it is permitted to sterilize a female pet through chemical sterilization. According to all it is forbidden to do so through removal or destruction of a reproductive organ. This applies whether one is doing it himself or is having someone do it for him.
 Michaber E.H. 5:11; Rambam Issurei Biyah 16:10; Chinuch Mitzvah 291; Shabbos 110b; Vayikra 22:24: “Ubeartzechem Lo Sasu.”
 Birkeiy Yosef 5; Sheilas Yaavetz 111, brought in Pischeiy Teshuvah 5:8; See Minchas Chinuch 291:1
 The reason: The verse [Vayikra 22:24] states “Ubeartzechem Lo Sasu” and from here we learn of the prohibition against castration. [Shabbos ibid; Rambam Issurei Biyah 16:10] The reason behind this prohibition is because G-d created the world in perfection and desired the continuity of each of his creations and commanded them to procreate. One who castrates a creature reputes G-d’s creation and is doing an act of destruction to his beautiful world. [Sefer Hachinuch Emor 291]
Does the prohibition of castration apply to an old man who can’t have children? See Otzer Haposkim 5:64
 Otzer Haposkim 5:63
 Michaber ibid “One who castrates a female is exempt from lashes although it is forbidden to do so”; Rambam Issurei Biyah 16:11; Magid Mishneh on Rambam ibid; Shabbos 111a “Ela Beisha”; Toras Kohanim on Vayikra 22:24 in name of Rebbe Yehuda “There is no castration by females”
Other opinions: Some Poskim rule there is no “castrating” prohibition to castrate a female human:creature, although it is forbidden to cause her pain against her will, or for no need, due to a separate prohibition of Tzaar Baalei Chaim. [Taz 5:6 in interpretation of opinion of Rebbe Yehuda ibid]
 So is the general rule of “Patur Aval Assur” that it contains a Rabbinical prohibition. [See Rambam Shabbos]
Other opinions: Some Poskim rule that the Michaber and other Poskim rule like the first opinion in Toras Kohanim ibid that the prohibition is Biblical even by a female, although one is exempt because they are not included in the Lo Sasei of Lo Sasu. [Gr”a ibid]
 The reason: Castrating a female does not carry Biblical liability being they are not commanded in Peru Urevu. [See Rashi Shabbos ibid] Alternatively, the reason is because their reproductive organs are inside the body and hence cannot be destroyed with direct action. [Taz 5:6] Nevertheless, it is still forbidden to castrate them as even women are commanded to populate the world due to the verse “Lo Letohu Bara Ela..” [Perisha 5; The Taz 5:6 negates this explanation of the Perisha, as if so then it would be forbidden for her to take chemical sterilization.]
 Michaber ibid; Shabbos 111a
 The reason: The reason is because the verse states “Umauch Vekasus.” [Shabbos ibid, brought in Taz ibid, unlike Perisha] Alternatively, the reason is because the verse states “Lo Sasu” in plural. [Perisha, brought in Taz 5:5]
 Tzaruch Iyun as to the differences between “detaching” and cutting”.
 Rav Chidka and Tana Divei Menashe in Sanhedrin 56b and in Bava Metzia 90a rule that one of the seven Nohadite laws is not to castrate [they remove the prohibition of Birchas Hashem and replace it with Sirus], and hence gentiles are commanded against castrating, just like they are commanded to follow the other Nohadite laws; However, the Tana Kama in Sanhedrin ibid rules that gentiles are not commanded against castrating. [As they list Birchas Hashem as one of the seven Nohadite laws, which thus excludes the prohibition of Sirus from being included.]
 Implication of Michaber E.H. 5:14 and Stam opinion in Rama ibid, who permits selling to a gentile even if one knows that he will castrate [See Chelkas Mechokeik 5:8]; Rambam; Rosh [brought in Chelkas Mechokeik ibid]; Rashba; Hagahos Maimanis, brought in Beis Shmuel 5:16; Minchas Chinuch Mitzvah 291 in opinion of Rambam and Chinuch. Chelkas Mechokeik 5:8 concludes that we rule like this opinion, as so rule vast majority of Poskim; [The Chelkas Mechokeik ibid explains that the final understanding of the Gemara Bava Metzia ibid is what determines whether we hold like Rav Chidka or not, disputed as, and all those who rule that the prohibition of Amira Lenachri applies to all Issurim, dispute the ruling of Rav Chidka, and since the final ruling in the Shulchan Aruch follows that Amira Lenachri applies in all cases, it is a proof that we do not rule like Rav Chidka, and if so, then the Rama should not have recorded this opinion.] Gra 5:37 “We do not rule like Rav Chidka, as write all the Poskim”; Aruch Hashulchan 5:26 writes that most Poskim rule gentiles are not commanded, and so is the main Halacha, although some are stringent.
 2nd opinion in Rama ibid who forbids selling an animal to a gentile, as explained in Taz 5:10, Chelkas Mechokeik ibid and Terumos Hadeshen 299; Semag; Hagahos Ashri, brought in Beis Shmuel 5:16; Raavad, brought in Rosh, brought in Chelkas Mechokeik ibid
 Beis Shmuel 5:16; 18; brought in Aruch Hashulchan ibid
 Minchas Yitzchak 5:13; Nishmas Avraham 5:11
 See Otzer 77; Nishmas Avraham p. 113
 Igros Moshe E.H. 4:34
 Yabia Omer E.H. 9:11
 Michaber E.H. 5:12; Based on Shabbos 110b
 Ramach, brought in Beis Yehuda 2:47 and Birkeiy Yosef 4:10
 The reason: Since no physical action was done to the limbs therefore there is no punishment of lashes. [Beir Hagoleh]
 Beis Shmuel ibid
 Ritva Yevamos 63, brought in Birkeiy Yosef 5:13; He writes there that so was done by Gedolim; Birkeiy Yosef ibid questions his ruling based on Shabbos 110, although concludes that it can be answered
 Beis Shmuel 5:13
The reason: As it is a Pesik Reishei, of which we rule it is forbidden. Now, although regarding Shabbos we permit a Pesik Reishei Delo Nicha Lei, nevertheless, by other prohibitions this is forbidden. [Beis Shmuel ibid, based on Rosh; Ran]
 Birkeiy Yosef 5:12 in name of Ritva; Zera Avraham 1, brought in Pischeiy Teshuvah 5:9
 Ramach, brought in Beis Yehuda 2:47 and Birkeiy Yosef 4:10
 Beis Yehuda 2:47, brought in Birkeiy Yosef 4:10
 Zera Avraham E.H. 11; Mahariy Shushan p. 144 Responsa 56; Yad Ahron; Birkeiy Yosef 4:7
The reason: As the prohibition only applies if the reproductive organs are physically damaged, mutated or deformed. [Birkeiy Yosef 4:8]
 Michaber ibid; Chinuch Mitzvah 291
 The reason: As a woman is not commanded to have children. [Chinuch ibid]
 Chelkas Mechokek 5:6; Beis Shmuel 5:14; Taz 5:7; Birkeiy Yosef 5:14 in implication of Michaber and Rambam; Semag L.S. 120; Implication of Chinuch Mitzvah 291; See Chasam Sofer in next footnote who differentiates between if she has children or not
The reason: As this does not involve any action at all. [See Beis Shmuel ibid]
 Bach 5, brought in Chelkas Mechokek ibid and Taz ibid; Rashal in Yam Shel Shlomo 44, brought in Birkeiy Yosef ibid; Sefer Atzei Razim, brought in Chasam Sofer 20; The Taz ibid negates the reasoning of the Bach; Chasam Sofer ibid, brought in Pischeiy Teshuvah 5:11, concludes that a woman who does not yet have children is not to drink a sterilizing chemical unless she is doing so to prevent pain. If, however, she has children, she may drink it whenever she wants, even without pain; The Taz ibid negates the reasoning of the Bach
 Rashal ibid; Seemingly the same would even more so apply to physically unhealthy children
 Chelkas Mechokek ibid
 Chasam Sofer 20, brought in Pischeiy Teshuvah 5:11
 Chelkas Mechokek 5:6; Beis Shmuel 5:14; Semag L.S. 120
 See Bach; Chelkas Mechokek ibid; Possible implication of Michaber ibid who writes by the prohibition “animals, and by the allowance “women”, and not “male animals” and “females”
 The reason: [brought in Chelkas Mechokek ibid]
 Michaber E.H. 5:13
 Beis Shmuel 5:15
 Michaber E.H. 5:14
 Literally “Kutti”
 The reason: This is forbidden due to Amira Lenachri, as every matter in the Torah that is forbidden for a Jew to perform is likewise forbidden for a Jew to ask a Gentile to do for him. [Beis Shmuel E.H. 5:16; Beir Hagoleh; Shach Y.D. 141:17 and 23; Admur 243:1; 343:5; 450:20; Ribis 72; Sheila Usechirus 29; Michaber C.M. 338:6 [regarding muzzling animal]; Question brought in Bava Metzia 90a and above Poskim rule stringently-see Biur Hagr”a 5:32] Alternatively, the reason is because it is Biblically forbidden for even a gentile to destroy the reproductive organs of a human:animal, and it is part of the Nohadite laws. [Beis Shmuel 5:16; Rav Chidka in Bava Metzia 90a and Sannhedrin 56b]
 Michaber E.H. 5:14