Some of your horses need to be taken care of, the metal bucket icon. You need to feed/water your horses so that they are 100% health, otherwise you cannot make them run “hungry” and “thirsty” the others? Have 0% energy and you gotta wait until their energy refills back up to 100%

So, if you still need help, just caring for your horses isnt enough. :) To enter them in Halter Shows, you need to Register them with a club or their breed registry. Discipline shows can be done with any horse 2yrs and up by setting a discipline in the “Edit Horse” page. Halter shows can be done with any horse that is registered and has finished foal training.

You can see at the top of their page, just under their name, if they are a Crossbreed, Grade, or Purebreed. It wont say Purebreed, but itll say a breed instead of grade/crossbreed (i.e Percheron, Appaloosa, Harlequinn Warmblood, ect.)

Crossbreed >> No Breed Registry, Yes Clubs.
Grade >> No Breed Registry, Yes Clubs.
Purebreed/Campaign >> Yes Registry, Yes Clubs.

IDK if that made sense, but i hope it helps. :) Also, you can find both Breed Registries and Clubs under the Town tab. EDIT: I forgot to mention that you do have to also be a part of the breed registries to do Halter shows. The fee to join can range, as can the fee to register horses

And grade breeds like Grade Friesians or Grade Clydesdales can't be halter shown but they can enter discipline or careers. Same with crossbreeds, unless they're a recognised crossbreed such as the Walkaloosa. If you horse just says ‘Crossbreed’ or ‘Grade Breed' then they can't be halter shown :)