I think that is not possible for the MyStable team to do. Imagine hundreds of players are going on a holiday, and the MyStable team will have to go to each of the player's stable block and feed and groom the horses. The new system is coming up soon on the game once the MyStable team finish working on it. Besides, it'll be much better for them to work on the new system rather than feed or groom each player's horses when they are on holiday!