I'll give horses and llamas wheat, and eventually they won't let me give it to them anymore, and if I exit my current game and go back in the wheat shows back up and no matter how much I give, the animal won't tame.

Edit: I have tried riding the animals after I give them wheat but no matter how much I give them, it doesn't work and eventually they wont let me try to ride them anymore. I have tamed horses and donkeys before on Minecraft, and now it is not working the same as it did before.