Creation is meant to increase life in the world, as it is stated after the creation of the fish and birds (Bereishit 1:22): “God blessed them, saying: Be fruitful and multiply.” In keeping with this, the Torah prohibited the act of sterilization – that is, any act that damages one of the reproductive organs of a person, domesticated animal, wild animal, or bird. Anyone who sterilizes any of these violates a Torah prohibition punishable by lashes (Vayikra 22:24; SA EH 5:11).
The Torah prohibition of sterilization was stated regarding males, whose reproductive organs are exposed and who were the ones normally sterilized. According to most poskim, however, sterilizing females is prohibited rabbinically. Some maintain that sterilizing a female is also prohibited by Torah law, though one does not receive lashes for sterilizing a female. Others maintain that there is not even a rabbinic prohibition against sterilizing females; rather, because sterilization involves great pain, it is forbidden on account of the suffering it causes. According to this view, if they were sterilized without suffering, there would be no prohibition.
In recent times, animal-welfare organizations have become concerned with the problem of street cats. With no predator to reduce their numbers, they have multiplied greatly; the food discarded in garbage bins is insufficient for them, and they roam hungry and emaciated, crying from distress and trying to sneak into homes to still their hunger. Some suggested trapping male cats and sterilizing them by cutting the ducts that carry sperm. The cats would then be marked by clipping part of the ear, so that they would not be trapped again by mistake. Once about eighty percent of the males were sterilized, the overwhelming majority would be unable to impregnate females, and the cat population would gradually decline.
However, as we have learned, sterilizing the male cats is prohibited by Torah law. It is also forbidden to hire gentiles to do it, because whenever an act is forbidden to Jews by Torah law, the Sages prohibited Jews from asking a gentile to perform it (SA EH 5:14). In addition, some maintain that Bnei Noaḥ too are forbidden to sterilize animals. According to this view, asking them to sterilize cats would be prohibited by Torah law, since we are commanded not to cause another person to stumble in sin. Sterilizing females is also forbidden by rabbinic law according to most poskim. A possible non-sterilizing solution is to periodically place appealing bait containing contraceptive medication in the streets. This would prevent the female cats from ovulating and going into heat, allowing the cat population to gradually decline without violating the prohibition of sterilization.
The same approach should be used when a person does not want his dog to become pregnant: he should give the dog contraceptive medication. Although there is concern that such medication may cause illness, it remains the proper halakhic solution. Just as contraceptive medications were developed for human beings without causing illness, similar medications could be developed for animals as well. In pressing circumstances, since many authorities maintain that sterilizing a female animal is prohibited only rabbinically, there is room to permit a Jew to sterilize a female dog or cat indirectly, such as by injection or by blocking the fallopian tubes. This is a form of grama, an indirect act whose sterilizing effect takes place only later. The more straightforward solution, however, is for a gentile veterinarian to perform the surgical sterilization.[10]
[10]. It is generally forbidden to ask a gentile to sterilize an animal. This is clearest when the act itself is prohibited by Torah law, as in the sterilization of a male animal. According to most poskim, the Sages prohibited asking a gentile to perform any act that is forbidden to a Jew by Torah law: just as a Jew may not ask a gentile to desecrate Shabbat, he may not ask a gentile to violate other Torah prohibitions. Although Ra’avad is lenient regarding this general rule, most poskim are stringent, including Rambam, Rosh, Nimukei Yosef, Rashba, and Ran, and this is codified in SA EH 5:14 (see Peninei Halakha: Shevi’it 5, note 9).
There is an additional concern. In Sanhedrin 56b and 57a, the Tanna of the school of Menashe and R. Ḥidka maintain that Bnei Noaḥ are also prohibited from sterilizing animals, based on the verse: “Swarm upon the earth and multiply in it” (Bereishit 9:7). According to the Sages, however, this verse is a blessing, not a command. Most Rishonim rule like the Sages, including Rosh, Bava Metzia 7:6; Nimukei Yosef, Bava Metzia 53a; Beit Yosef, EH 5; and Bi’ur HaGra, in the name of the poskim. She’iltot, Emor §105, however, maintains that Bnei Noaḥ are also prohibited from sterilizing animals, and this is also the view of Semag, Lavin §120, and Or Zaru’a, Bava Metzia §286.
The status of sterilizing females differs from that of sterilizing males. According to the Vilna Gaon, EH 5:25, sterilizing a female is prohibited by Torah law, though one does not receive lashes for it; he derives this from Torat Kohanim. According to most poskim, however, the prohibition is rabbinic, since the female reproductive organs are internal and the primary obligation of procreation rests upon males. This is implied by Rambam’s language (MT, Laws of Forbidden Relations 16:11), as understood there by Maggid Mishneh, and it is also the view of Ramban, Rashba, Ritva, Ra’ah, Ran, Me’iri, and many Aḥaronim. Taz, EH 5:6, is more lenient still, maintaining that there is no independent prohibition against sterilizing females; the prohibition is only because of the suffering involved. Some Aḥaronim therefore write that when there is a genuine need, one may be lenient if the procedure is performed by a gentile, since this is a shvut di-shvut in pressing circumstances or for the sake of a mitzva. Accordingly, in such a situation, when there is a significant need to sterilize a female dog or cat, the most straightforward practical solution is for a gentile veterinarian to perform the procedure. If that is not possible, there is room to permit a Jew to sterilize the female indirectly, such as by injection or by blocking the fallopian tubes, provided it is done as grama — an indirect act whose sterilizing effect takes place only later. When contraceptive medication can solve the problem without causing illness, it is preferable.
