This is a very broad category, and different laws apply to each type of animal.

Further reading: The source for the halakhot of kashrut for animals can be found in A Concise Guide to the Torah, pp. 272, 468.

All invertebrates are prohibited for consumption. The prohibition includes mollusks, snails, oysters, crabs, and all species of insects, spiders, arthropods, and many more.

There is one exception: In principle it is permitted to eat certain species of grasshoppers. In fact, eating grasshoppers was (and still is) accepted among the members of a few Jewish communities, particularly Yemenite and North African Jews. In other communities, however, the eating of any kind of grasshopper is avoided.

The prohibition against eating insects includes substances that come from their bodies. Nevertheless, it is permitted to eat the honey of bees. This permission, which can be traced to biblical sources, is based on the fact that the honey is not fully produced by the bees: It is essentially flower nectar that is broken down by an enzyme in the bee’s saliva, and thereby turns into honey. Pure honey does not require kosher certification, provided that it is free of admixtures.

Considering the prohibition against eating bugs, one must carefully examine vegetables and grains in which various types of worms and insects are likely to be found. It is especially necessary to examine herbs, lettuce, cabbage, cauliflower, and dried fruits. One should seek guidance in how to ensure that one’s vegetables and fruits are bug-free.

Leafy vegetables: Where available, it is best to purchase vegetables that have been specially grown in a manner that allows them to be relatively free of bugs, such as in the greenhouse system developed in Gush Katif. These vegetables are separated from the ground soil, which greatly reduces the incidence of bugs in the vegetables.

Sifting flour: Insects can often be found in flour and similar substances. The most common of these is the flour beetle. Proper pest control can prevent the insect from multiplying, but any insects that are already in the flour must be removed by thorough sifting.

Rice and beans: There can also be insects in rice and other grains. The usual sign for the presence of larvae is webbing and clumping. One must examine the grains carefully to make sure that they contain no insects. In the case of chickpeas and beans, it is recommended to perform the examination after they have been soaked in water and have swelled.

Amphibians: Frogs, toads, and the like are all prohibited for consumption.

Reptiles: All types of lizards, snakes, and turtles are prohibited for consumption.

Fish: The Torah distinguishes between kosher and non-kosher species of fish: Fish that have fins and scales are permitted to be eaten, whereas fish without fins and scales are forbidden. This division overlaps to a large extent, though not absolutely, with the zoological division between Osteichthyes, bony fish whose skeletons are primarily composed of bone tissue and which are permitted for consumption, and Chondrichthyes, whose skeletons are made of cartilage rather than bone, most of which are predatory fish, and which may not be eaten.

Most fish that people eat are halakhically permitted for consumption. One can perform a simple test to see if a fish is kosher, by examining whether it has scales. A fish that has visible scales, which can be removed from its skin, is kosher.

Sharks, catfish, and eels are not kosher.

There are several species of fish whose status in Jewish law is unclear, and sometimes the practical question of whether one may eat them or not depends on the local custom.

The distinction between kosher and non-kosher fish, as with all animals, includes all their by-products, from fish oil to caviar. Some types of caviar are kosher while others are not; it depends on the fish from whose eggs the caviar is made. For example, one should not eat black Russian caviar, which is produced from the sturgeon, a non-kosher fish.

All other water creatures are prohibited for consumption, including, as noted, crabs and clams, and, of course, marine mammals, from seals to whales. All products produced from these marine mammals are prohibited as well.

Unlike animals and poultry, there are almost no halakhic problems with regard to kosher fish. It is permitted to kill fish in any manner, and it is permitted to consume their blood as well. The reason it is permitted to consume the blood of fish, unlike the blood of kosher birds and animals, is that the verse states: “And all blood you shall not eat in any of your dwellings, of bird or of animal” (Leviticus 7:26), with no mention of fish.

It is permitted to eat fish as part of either a meat or a dairy meal. Nevertheless, one may not cook fish and meat in the same pot, nor eat them together. Rather, one should take a short break between fish and meat dishes, by having a drink or something similar.

There are many kashrut considerations pertaining to poultry, and each requires a separate discussion.

The first factor is the identification of permitted and prohibited birds. The Torah provides a list of non-kosher birds, but not all species in the list can currently be identified with certainty. Although the Sages provided certain signs of kashrut for various birds, in practice the number of species of birds that one may eat without concern is quite limited. These include certain common domestic birds: chickens, turkeys, geese, ducks, and pigeons.

After one has confirmed that the bird is indeed kosher, there are a few steps one must perform before it may be eaten. The first of these is slaughter.

Nowadays, the slaughter of birds is carried out by professional ritual slaughterers who have the appropriate certificate from an authorized rabbi, attesting to their knowledge of the halakhot as well as their practical skills. Apart from performing the act of slaughter itself, an expert must ensure that the bird is not afflicted with a wound or sickness that renders it a tereifa. Furthermore, if something goes wrong during the process of slaughtering, the slaughter is disqualified and the bird is defined as a neveila, an unslaughtered animal carcass.

In summary, halakha permits the eating of kosher birds, provided that they are healthy and are slaughtered according to Jewish law.

Next, the bird must be “kashered,” or rendered kosher, which involves removing its blood to the maximum extent, as the Torah prohibits consuming the blood of poultry and land animals. Kashering is performed by salting the meat and washing it in water. Today, most of the poultry and meat that is sold in supervised shops and markets which have kosher certificates has already been salted properly in the slaughterhouse or in an adjacent facility, and there is no need to do anything further to render it kosher.

Further reading: The sources for the prohibition against consuming blood can be read in A Concise Guide to the Torah, p. 466.

Raw liver cannot be kashered by salting. Therefore, even if it is purchased in a kosher butcher shop, one must kasher it by sprinkling a little salt on it and roasting it on a fire to remove its blood. Then one should rinse it in cold water. If liver that has not been roasted in fire was cooked in a pot, it renders the pot non-kosher.

With regard to hearts, there are different opinions, and one should consult a rabbi.

Eggs: Eggs may be eaten only if they come from kosher birds or fish. The eggs of non-kosher birds and reptiles are prohibited.

Most of the eggs sold today are non-fertilized, and they contain virtually no blood. Nevertheless, there can sometimes be blood in an egg, and this blood is prohibited for consumption. Therefore, it is advisable not to crack an egg directly into a pan or a dough; instead, it should be cracked over a bowl or a glass and the egg should subsequently be examined to ensure that it is free of blood. Only then may one use it in cooking.

Mammals: The Torah states that animals that chew their cud and have cloven hooves may be eaten, whereas animals that lack both or one of these characteristics may not be eaten. Among domesticated animals one may eat cattle, sheep and goats, while among the non-domesticated animals one may eat all types of deer and gazelles, which constitute a defined zoological family. All other mammals are prohibited, and from a halakhic point of view, there is no difference between the prohibitions of eating a horse, a camel, or a pig.

As is the case for birds, one must observe the laws of ritual slaughter and tereifa with regard to mammals. An animal that was not properly slaughtered, or which is classified as tereifa, may not be eaten.

There are more incidences of tereifa in mammals than in birds, and therefore, after their slaughter one must conduct a more comprehensive and thorough examination.

In this regard, there are those who are careful to eat only meat that is “glatt,” literally “smooth,” i.e., meat with regard to which no questions arose during its slaughter or subsequent examination, and which is therefore kosher according to all opinions.

Further reading: For more on the various levels of kashrut and their meaning, see p. 573.

There are other prohibitions that apply to the flesh of animals: the prohibition against eating specific fats, and the prohibition against eating the gid hanasheh, the sciatic nerve. There are professionals whose job is to remove these forbidden parts from the meat.

It is interesting to note that the ancient Chinese called the Jews who lived among them “the people who remove the nerve,” as an acknowledgement of their religious observance.

Further reading: This prohibition is in commemoration of our forefather Jacob’s wrestling with the angel, which is described in A Concise Guide to the Torah, p. 81.

There are some communities in which the hind parts of the animal (where the sciatic nerve is located) are not sold as kosher meat, either due to a lack of familiarity with the halakhot of removing the nerve, or because of the great effort that this procedure entails.

The meat of the animal must be kashered (see above) after the slaughter, to remove all of its blood.

Further reading: For more on eating meat and vegetarianism, see A Concise Guide to Mahshava, p. 122.