Horses cannot get druck from eating apples anymore than people can. However, if a horse eats too many apples they can colic because the apples will ferment and create gas. Horses cannot burp or vomit...
Most of them do, but it really depends on the horse. One may eat them until there is no more, while another could shun it completely. They also like carrots and, if used very moderately, peppermints....
Horse apples = manureYes, sometimes horses eat manure. This is called coprophagia. Foals start to eat manure at about two weeks of age. It is speculated that this is how they get good gut bacteria...
While a crab apple may not hurt your horse, too many crab apples can cause a horse to colic and/or founder. These are serious health problems, colic being the number one reason for emergency...