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
American Champion Male Turf Horse to create the Eclipse Award. From 1953 through 1978 it was awarded to male or female horses although the only female champion was Dahlia in 1974. In 1979 an individual category was created for each of the sexes. Starting with the 2015 Eclipse Awards it is no longer possible for a Champion Male Turf Horse to also win Champion Older Male Horse, as the latter category is now restricted to horses proficient in dirt or main track races. The last such winner of both awards was Main Sequence in 2014. Most wins: Most wins by a trainer: Most wins by