There is a mitzva to treat animals with compassion, and it is prohibited to cause them unnecessary suffering. At the same time, people may use animals for labor and food: donkeys and mules for carrying loads, oxen for plowing, horses and camels for riding, and animals for their meat. The Torah goes further still, commanding us to offer animal and bird sacrifices, including the scapegoat and the heifer whose neck is broken. This is what the Sages meant when they said that animals were created to serve human beings (Kiddushin 82a; Sanhedrin 108a). Included in this is their use for food: just as animals may eat plants, human beings may eat animals.
These two values must therefore be balanced. On the one hand, human needs take precedence over the needs of animals. On the other, one must make every effort, as far as possible, to avoid causing animals to suffer. Thus, even when Bnei Noaḥ were permitted to eat meat, the Torah forbade the cruelty of eating a limb from a living animal.
In practice, when a human need conflicts with the duty to prevent animal suffering, one weighs how essential the human benefit is against the suffering caused to the animal. Eating meat, for example, is a very significant human need, and sheḥita causes only mild suffering (see below, 18:3); therefore one may slaughter animals for food. But when the human need is less essential, or when meeting it would cause the animal great suffering, the question becomes more complex. Halakha addresses such cases by weighing three fundamental principles:
The first principle concerns the degree of suffering: mild, ordinary, great, and extreme. The greater the suffering, the more serious the matter becomes; only rarely, for a truly essential need, is there room to be lenient.
The second principle concerns the animal itself. The more cognitively complex the animal, the more intensely it can experience suffering, and the more careful one must be not to cause it pain. This level of complexity is determined primarily by the animal’s brain and nervous system. Mammals, such as dogs, livestock, monkeys, and dolphins, have relatively complex brains and nervous systems: they visibly experience distress and joy, can be trained to some extent, and display maternal care, as a mother recognizes her offspring and tends to them with compassion. Even among mammals there are differences. A dog, for example, is more cognitively complex than a sheep; it can express certain emotions more clearly, and its suffering is greater when it is hurt. Below mammals are birds, followed by reptiles such as lizards, and then fish. Fish generally do not care for their young; indeed, only a few minutes after giving birth to small fry, a female fish may devour many of them without any sign of hesitation. Below fish are insects.
The third principle is that the more an animal serves human beings, the greater the compassion and fairness with which it must be treated. The Torah therefore commands us to help unload a donkey that has collapsed under its burden (below, section 2) and forbids one to muzzle an animal while it is working with food, thereby preventing it from eating (below, section 3). Accordingly, particular compassion should be shown to domesticated animals, such as cows, goats, sheep, and chickens. The same applies to dogs, which help guard the home, and cats, which rid the house of snakes and mice.
In summary: Ideally, one should not cause any living creature to suffer, even the lowest forms of animal life, as it is written (Tehilim 145:9): “His compassion extends to all His works” (see Bava Metzia 85a). When a person genuinely needs to cause animals suffering, each case must be weighed in light of the three principles explained above.[1]
[1]. Bava Metzia 32b: According to the Sages and R. Shimon, tza’ar ba’alei ḥayim is prohibited by Torah law; according to R. Yosei HaGelili, the prohibition is rabbinic. This also appears to be the view of Rabban Gamliel in Shabbat 154b. In Shabbat 128b, however, the Gemara assumes as a matter of course that tza’ar ba’alei ḥayim is prohibited by Torah law. This is also the view of the overwhelming majority of poskim, among them Rif, Ramban, Maharam of Rothenburg, Rashba, Rosh, Me’iri, Sefer ha-Ḥinukh, Tur, and Rema ḤM 272:9. The primary source for this is the mitzva to unload a donkey (below, section 2); according to Me’iri (Bava Metzia 32b), it is also derived from the prohibition against muzzling an animal (section 3). As for Rambam’s view in MT, Laws of Murderer and Preservation of Life 13:9, the matter is debated: most commentators understand that, in his view, the prohibition is rabbinic, but according to Radbaz and Kesef Mishneh, Rambam too maintains that the prohibition is by Torah law. Three principles define the prohibition and its severity.
The first principle: One must distinguish between different degrees of pain. In Shabbat 128b, since tza’ar ba’alei ḥayim is prohibited by Torah law, the Sages permitted violating rabbinic prohibitions to relieve it; but this dispensation applies only when the animal is suffering greatly. Similarly, Nimukei Yosef to Bava Metzia 32b and Ḥidushei Anshei Shem to Mordekhai, Bava Metzia 2, no. 40, write that one who causes an animal great suffering violates a Torah prohibition, while one who causes it minor suffering violates a rabbinic prohibition. Ritva and Tosafot ha-Rosh to Bava Metzia 31a write similarly: the mitzva to unload a donkey is by Torah law because of tza’ar ba’alei ḥayim, whereas the mitzva to help load it is by Torah law only because of the obligation to help another person. Although helping load the animal does relieve it of some suffering, relieving a small degree of animal suffering does not rise to the level of a Torah obligation.
The second principle: Since the mitzva is to prevent suffering, the law must take account of the differences between less cognitively complex creatures, which feel less pain, and more cognitively complex animals, which feel more. Indeed, one reason the Torah requires sheḥita for domesticated and wild animals is to reduce their suffering. Birds, which are less cognitively complex, require the cutting of only one siman. Fish and locusts, which are lower still in this respect, do not require sheḥita, and the prohibition of eating a limb from a living animal does not apply to them (Radbaz, Metzudat David §208; above, 14:6; below, 17:7–8). Similarly, She’elat Ya’avetz 1:110 writes that the prohibition of tza’ar ba’alei ḥayim does not apply to insects, although it is a pious practice not to harm any living creature unnecessarily. When there is a need, one may even kill rats that disturb people; the heavenly claim against Rabbi Yehuda HaNasi (Bava Metzia 85a) was because of the especially high standard expected of him personally (below, 18:3).
The third principle: The prohibition applies most severely to animals that serve human beings, such as a pack donkey or an ox used for threshing. Likewise, the requirement to provide animals with food (below, section 4) refers primarily to animals that serve people, such as livestock raised for meat and milk and birds raised for meat and eggs. She’elat Ya’avetz 1:110 writes similarly, adding that the Torah mitzva also applies to dogs, which guard the home, and cats, which rid it of snakes and scorpions. On a lower level, there is a mitzva to feed ownerless animals; if they are hungry, one may even exert oneself to feed them on Shabbat (below, section 15; AHS OḤ 324:2–3; MB 324:31).
