A Halachic Analysis of Spay/Neuter by Scott Sears, J.D.


I. Introduction

Many states and local governments have laws that require the spaying and neutering of animals.[3] In 2001, as a result of the New York legislature’s findings that there was an overpopulation of dogs and cats in New York, the public policy of New York State became that “every feasible humane means of reducing the production of unwanted puppies and kittens [shall] be encouraged.”[4] As such, any shelter, pound, or a few other similar organizations[5] that release animals must ensure that the dog or cat is spayed/neutered.[6]

In other places, such as Dallas, Texas and Los Angeles, California, there are spay/neuter ordinances which provide that all dogs and cats in the city must be spayed or neutered, with certain exceptions.[7]

In this article, I will analyze the issues involved in spay/neuter in Jewish law.

II. Processes of Sterilization

Spaying and neutering are surgical procedures performed by veterinarians that render animals incapable of breeding by removing their reproductive organs.[8] When a female dog is spayed (also called an ovariohysterectomy), the ovaries, fallopian tubes, and uterus are removed.[9] Neutering commonly refers to the castration of males and the complete removal of their testicles.[10]

According to Dr. Elizabeth Lynch, the way these surgeries are generally carried out is as follows[11]: female animals have an incision made just below the belly button into the abdomen.[12]  The reproductive tract, both ovaries, and the uterus are completely removed through this incision.[13]  Then the incision is closed with two layers of stitches under the skin that will dissolve and be absorbed by the animal’s body over time.[14] The skin is then closed with either skin glue, skin staples, or stitches.[15]

Male dogs have an incision made in the skin at the base of the penis nearest to the scrotum.[16] Both testicles are removed through this incision.[17]  The incision is closed with stitches under the skin that will dissolve and be absorbed by the body over time.[18]  The skin is closed with skin glue, skin staples, or stitches.[19] Male cats have an incision made in the skin of the scrotum, and the testicles are removed.[20]  The incision is not sealed, but closes on its own with time.[21]

In addition, there is a newer, non-invasive and non-surgical process of sterilizing male dogs referred to as “zeutering.” In this process, Zeuterin, a zinc-gluconate solution, is injected directly into a dog’s testicles.[22] This injection destroys all the sperm in the seminiferous tubules and in the epididymous, causing the seminiferous tubules to collapse.[23] Within days, scar tissue from the healing process creates blockages in the seminiferous tubules and the rete testis.[24] Over time, the seminiferous tubules, rete testis, epididymis, and prostrate will atrophy.[25] Sperm production stops within one to three days.[26] However, active sperm may still be in the vas deferens and epididymis for up to 30 days, and as such the dog may be able to impregnate up to 30 days after the injection.[27] This procedure is 99.6% effective in causing sterilization.[28]

III. Source of Prohibition

The Torah prohibits the sacrificial use of animals whose "testicles are bruised, crushed, torn or cut[29]," and further prohibits one from castrating any animal[30]. This prohibition applies to insects as well.[31] The sages understood this verse to prohibit sterilization of all male creatures, human and animals alike.[32]

A. Female Sterilization

The Torah verse forbidding sterilizing animals speaks specifically about male animals[33].  The Sifra[34] comments that this prohibition does not apply to female animals. The Rambam explains that while the sterilization of female animals is permitted on a Biblical level, the act itself is nevertheless prohibited on a Rabbinic level[35]. The Shulchan Aruch rules in accordance with this view of the Rambam.[36] However, according to the Vilna Gaon, this prohibition applies even to female animals on a Biblical level.[37] According to those that believe female sterilization is only forbidden on a Rabbinic level, there can potentially be more room for leniencies when it comes to spaying female animals, as explained below.

IV. Non-Jew

A. Non-Jew for himself/other non-Jew

The Talmud[38] records a dispute regarding whether the Torah forbids non-Jews to remove reproductive organs. The Rosh, Rashba, and the Rambam all rule that a non-Jew is not commanded in the prohibition of castrating animals.[39] On the other hand, the Smag and the Hagahot Oshri rule that castration is included in the Noahide laws that non-Jews are obliged to follow.[40] The Beit Shmuel[41] rules that because this controversy has not been resolved, one must act in accordance with the view that non-Jews are forbidden to remove reproductive organs. On the other hand, the Aruch Hashulchan[42] rules in accordance with the majority opinion, that non-Jews are not commanded concerning this prohibition.

A difference between the two opinions is that if non-Jews are included in this command, then instructing a non-Jew to remove reproductive organs would be a biblical violation of “do not put a stumbling block in front of the blind”[43], which prohibits enabling and encouraging others to sin.[44] The Rama rules that one can sell their animal to a non-Jew even if the non-Jew will definitely castrate the animal, although he notes that there are those that say that this is forbidden.[45]

B. For a Jew

The Talmud states[46] that if a Jewish person brings an animal to a non-Jewish veterinarian to be sterilized, the Rabbis penalize the violator and force him to sell his animal to someone else so that he does not benefit from his sin.  The Shulchan Aruch rules this way explicitly,[47] i.e. that it is forbidden to have a non-Jew to castrate an animal belonging to a Jew, and that if one does so, one must sell their animal.

                i. Possible Workaround

The Rama[48] says that although it may be forbidden to sell one’s animal to a non-Jew if one knows the non-Jew will castrate the animal, there is a workaround in which even those that forbid such a practice would allow an animal to be castrated. This is if the non-Jew that purchases the animal has another non-Jew castrate the animal.[49] The reason this is permitted is that there is no prohibition of enabling someone help someone else sin.[50]

The Chazon Ish[51] was asked if one can sell their animal to a non-Jew and instruct that non-Jew to have another non-Jew castrate the animal. The Jew would then buy the animal back from the non-Jew. The purpose of this procedure was to get around the penalty requiring one to sell their animal if they have their animal castrated,[52] as well as comply with the workaround of the Rama.[53] The Chazon Ish ruled that this practice is perfectly acceptable.[54]

Rabbi Chaim Jachter[55] notes that this ruling was given regarding animals used for commercial purposes. He points out that many contemporary halachic authorities[56] do not approve this method for household pets if done for convenience.[57] On the other hand, Rav J. David Bleich is of the opinion that this practice would be perfectly acceptable to be used for household pets as well, as there is no reason to distinguish between commercial animals and household pets.[58]

Given the lighter strictures regarding female species and claims of significant health benefits, Rav Shlomo Aviner allows a Jewish veterinarian to spay female pets,[59] and Rav Shmuel Vosner[60] does not protest having a non-Jew perform the procedure for a female animal, although he suggests one should avoid doing so. Sephardic Chief Rabbi Shlomo Amar has reportedly contended that because of public safety concerns from wild and ownerless animals, one may ask a non-Jewish veterinarian to spay and neuter pets of both genders.[61] The common practice, however, seems to forbid spaying and neutering animals.

V. Method of Castration

                A. Spay/Neuter

The Shulchan Aruch says explicitly that removing the reproductive organs of animals is completely forbidden, for males on a Biblical level, and for females on a Rabbinic level.[62] As such, the classic methods of spay/neuter is completely forbidden under Jewish law.

                B. Zeutering

Another method of sterilization mentioned in the Shulchan Aruch is by having the animal drink a substance that causes it to become sterile.[63] This method of sterilization is only forbidden for males and is completely permitted for females.[64] Some hold that this form of sterilization for males is forbidden on a Biblical level, while others maintain that it is only Rabbinically forbidden.[65]

Zeutering seems directly analogous to drinking a potion: In both cases the reproductive organs are not fully removed, yet the animal is rendered sterile. There are two possible differences, though, that may have significant halachic ramifications. The first is that zeutered animals can still reproduce for 30 days after injection.[66] As such, one can argue that this is only gramma, which though forbidden in many instances, provides room for leniencies in certain situations.[67] However, though not directly mentioned, one can assume that whatever substance referred to in the Shulchan Aruch would not cause instantaneous sterilization – it would presumably first need to be digested, which may take some time. As such, the fact that it takes time before the animal is rendered sterile after being zeutered likely would not have a halachic impact.

The second difference is that zeutering is 99.6% effective.[68] Though statistically improbable not to work, this possibility knocks zeutering down from an act of sterilization to a psik reishei. Though sterilization using a psik reishei is still completely forbidden,[69] it likely would knock down the prohibition from a Biblical to a Rabbinic level according to those that are of the opinion drinking the substance is Biblically forbidden.


Though advocated as public policy, it seems the vast majority of halachic authorities do not approve of spaying/neutering all cats and dogs. Therefore, unless a halachically approved way of spay/neuter becomes available, the general halachic view remains in opposition to the public policy on the issue of spay/neuter.[70]


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