Kraft, the maker of Jell-O, asserts that horse hooves are not included in Jell-O products. The hooves do not contain the collagen necessary to create the gel-like consistency of Jell-O.
The hides, bones and skins of pigs and cows are, however, used to make Jell-O. These substances are boiled so the collagen is released. The collagen is then filtered and ground into a powder. Since the animal products have been very heavily processed, they are not considered a meat or animal product by the federal government. However, vegans avoid Jell-O completely, as they do not eat animal products in any form.