Halacha forbids one from causing any unnecessary pain or distress to an animal
The Gemara (Bava Metzia 32b) presents a difference of opinion regarding the source of this prohibition, whether from the Torah or from Rabbinical decree.
- Bemidbar 22,32: “And the angel of HaShem said to him (Bilaam) why did you strike your donkey?” We should not follow the ways of the cruel ones that cause harm without human benefit.
- Shmos 23,5: “If you see the donkey of someone you hate lying under its burden, you should not refrain from helping him, but you should surely unburden (the animal) with him.” Per the Gemara (Shabbos 128b) this is a source that one should not allow pain to an animal.
- Devarim 25,4: “One shall not muzzle your ox when threshing (the field).” An animal would be distressed when it works with food and cannot eat it.
- Tehillim 145,9: “And His Mercy is upon all His creations.” From here we understand that the law of causing harm to an animal is a Torah-level commandment.
- Some state that this Mitzvah is a received tradition from Moshe at Sinai.
- Others say this is a decree from the Rabbis in order that we conduct ourselves with G-d’s world correctly.
The Talmud specifically states that Moshe was chosen for his mission because of his dedication in caring for animals. Rivkah was selected as a wife for Yitzchak after she displayed caring by watering the animals. On the other hand, the two hunters in the Torah, Nimrod and Esav, are both depicted as villains.
For Human Benefit
The prohibition of Tza'ar Balei Chayim is suspended, when the distress results from an action that prevents some benefit to a human. It is surely permitted to place a yoke on an ox to plough a field, or to make an animal carry a load. Animals were created for the purpose of mankind, and therefore man's needs take precedence over Tza'ar Balei Chayim (Shulchan Aruch, Even Ha'ezer, 5:14).
On this basis, contemporary Poskim (see Tzitz Eliezer, 14:68) permit medical testing and research on animals, seeing as there is a clear benefit to humans. Although if this can be done in a painless way (such as by administering an anesthetic) it is preferable.
Nonetheless, Shulchan Aruch (ibid) says that it is customary from refraining from such activities as plucking feathers from a live duck, even though there may be some benefit to a person, because it is deemed unnecessarily cruel. Furthermore, R' Moshe Feinstein (Igros Moshe, Even Ha'ezer, 4:92) limits this permit when of benefit to man, only where it is apparent and genuine. To force-feed an animal, for example, simply in order for the meat to appear to be of better quality, when in fact there is no actual difference, is forbidden, because such dubious benefit does not justify Tza'ar Ba'alei Chayim.
Fish
Although this prohibition applies to birds as well as animals, interestingly, Si'ach Yitzchak (387) points out that there would appear to be no such prohibition with regard to fish.
Tza'ar Ba'alei Chayim to Humans?
Does the Mitzvah of P'rikah, unloading a struggling animal, apply to people as well?
Chavos Ya'ir (191) rules that the mitzvah does not apply. The animal was loaded up without having any say in the matter, but a person has intelligence, and if one chose to overload himself, there would be no mitzvah to help him unload the burden. Birkei Yosef (Yoreh De'ah, 372:2) quotes this same idea but notes that if the reason would not apply (for example, the man was made to carry the burden against his will) these authorities would agree that the mitzvah would then apply.
However, the consensus of the Poskim (Rambam, Sefer HaMitzvos, 203; Sefer Hachinuch, 541; Rashb"a, I:252) appears to be that the Mitzvah of P'rika applies to people as well. Sm"a (272:13) writes that although this concept does not appear in the Gemara, the Rambam understood that if the Torah instructs the Jew to be concerned for the pain and distress of an animal, it surely follows that the Torah would be likewise concerned for the distress of the Jew himself!
