Hinny is easier to obtain when the lower chromosome count, the donkey, is in the male. Therefore breeding for hinnies is more hit-and-miss than breeding for mules." The male hinny or mule can and will mate, but the emission is not fertile. Male hinnies and mules are usually castrated to help control their behavior by eliminating their interest in females. Female hinnies and mules are not customarily spayed, and may or may not go through estrus. Female mules have been known, on rare occasions, to produce offspring when mated to a horse or donkey, although this is extremely uncommon. Since 1527,
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