Horse breed been produced. Such restrictions have led to legal challenges in the United States, sometime based on state law and sometimes based on antitrust laws. Horses can crossbreed with other equine species to produce hybrids. These hybrid types are not breeds, but they resemble breeds in that crosses between certain horse breeds and other equine species produce characteristic offspring. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, the hinny, is a cross between a stallion and a jenny (female donkey). Most other hybrids involve the zebra (see Zebroid). With
A Donkey, 3 Rocks, and a Bird. facing one another. The donkey has a rock balanced on its back, while the bird is both standing on a rock and balancing one on its head. The donkey has surfaces decorations, including glyphs and figures, and is coated in polychrome bronze. The bird is coated in blue, green, orange, red and yellow. The sculpture measures approximately x x . Its base is made of exposed aggregate concrete and measures approximately x x . One plaque on the base reads, . Another reads, . Inscriptions near the donkey's crotch displays the artist's last name, a copyright symbol, and the year