In the UK and Europe they have often been feeding a diet like muesli (here it is a people breakfast food) which here in the US has been frowned upon. We feed hay, hay, hay, and rabbit pelleted feed. They have just published findings that the muesli formulation is not good for rabbits.
The University of Edinburgh in the UK has linked muesli-style foods to life-threatening dental and digestive problems in rabbits. Veterinarians have suspected for a number of years that feeding muesli-style foods could lead to health issues in rabbits. There is now
evidence to support this theory, leading retailers to remove muesli-style
rabbit food from their shelves.