Animal by-products include: leather, wool, feathers, bone (for products such as gelatin), intestine and catgut (for sausage casings, instrument strings, rennet for cheese manufacture), hair (for brushes and furniture padding), blood (for animal feedstuffs), animal fats and lycerine (in confectionery and cosmetics). In addition to these more obvious products, many others are used in the manufacture of consumer goods considered essential to life although no mention of the animal origin is made on the label. Animal products are also widely sort as status symbols (rhinoceros horns as dagger handles), as trophies (animal heads, antlers, skins), as collectors items (birds eggs), as aphrodisiacs (horn), and as fashion accessories (fur).
In China, donkey skins are boiled to produce a brown gelatine, which is the essential ingredient in Chinese "ejiao" products - popular health foods and traditional medicines; ejiao gelatine can sell for up to $388 per kilo. China's donkey population dropped from 11m in 1990 to 3m in 2017. Suppliers now import skins from elsewhere, particularly Africa where the animals are such an important part of life for transport and farming in poorer communities. 1.8m skins are traded every year - according to estimates from UK-based charity The Donkey Sanctuary - but the demand is as high as 10m. Uganda, Tanzania, Botswana, Niger, Burkina Faso, Mali, and Senegal have banned donkey exports to China.
There is no such thing as an innocent animal by-product. Even in the case of wool, although sheep are not slaughtered after the first shearing, some 40% of sheep and lambs are as part of the economic pattern of sheep farming. The availability and cost of wool are dependent on the slaughter of sheep. By changing habits and diet to avoid animal products, a major step is taken towards the elimination of cruelty to animals. By purchasing clothes and accessories of non-animal origin, people deepen their commitment to animal rights and non-violence.
Animal by-products are a natural by-product of the animal, especially in the case of such products as wool, and do not cause the animal's death. Such use may constitute a wise recycling of natural resources. They may also reduce the cost of associated meat products for human consumption.