Rabbits need foods that contribute to a luxurious fur, but this goal must be weighed against controlling fat intake. Typically, these pellets are low in fiber and higher in fat and protein. Rabbits are herbivores. Herbivores have developed evolutionarily to consume plant material as the primarily component of the diet. The digestive tract of herbivores is also specialized.
Rabbits are no exception.
Their digestive tract includes a significant hindgut, including the cecum, which is the first part of the large intestine, except it is dilated and ends bluntly. The cecum is where most of the fermentation of fiber by microbes occurs. The volatile fatty acids are absorbed by the rabbit and provide energy. All of this action is accomplished by peristaltic contractions of the gut, which move food, divide and separate it, and produce cecotrophs, or night feces. The consumption of night feces by the house rabbit may appear as a vile and grotesque habit, but it is completely normal.