I tamed a horse and a donkey and wanted to breed them, so i mounted the horse and right clicked it with wheat. (several times with different horses/donkeys)
What I expected to happen was...:
The weat being consumed and hearts coming out of the horse. Then when i'd do both they'd breed.
What actually happened was...:
Nothing, the wheat stayed and no hearts came out, the animals didnt breed.
Steps to Reproduce:
1. Tame a horse
2. Get on it (i tried it with and without saddle)
3. Rightclick on the horse with wheat *
*I am not sure if you would be able to reproduce the bug since others dont seem to have the same problem, although they might be playing on a snapshot instead of 1.6 pre-release