Rabbits are obligate herbivores designed to consume large amounts of plant material which is high in indigestible (lignified) fibre. They should be fed on good hay, fresh grass, wild plants, herbs, dried grass, good grass or hay based pellets supplemented with vegetables, a little fruit as a treat and willow, fruit or hazel twigs to strip.
Their wild diet consists of grasses and wild plants supplemented with roots and bark when food is scarce. Their teeth grow continuously and need the constant chewing action involved in eating 100 small meals a day, and the abrasive action of the mineral rich fibre against their teeth, to keep them ground down to a suitable length.
High Fibre Diet
The rabbit’s digestive system depends on the indigestible fibre in the diet to keep keep food moving through the gut at the right speed. Too fast and the rabbit cannot digest food, too slow and the pH of the gut starts to favour disease causing bacteria instead of the friendly bacteria that help the rabbit break down digestible fibre, protein and carbohydrate.
Check the analysis of many of the rabbit foods on the market and although the Small Animal Veterinary Association recommends a diet high in fibre with a lower level of protein, many rabbit foods do not have enough fibre or have too much protein in relationship to fibre.
All fibres are not equal
The length of fibre is also important, finely powdered plant material cannot be used as indigestible fibre. The minimum length of fibre used in rabbit pellets should be 2.5mm. Unfortunately, manufacturers of rabbit feeds are only required to list total fibre in the declared analysis.
There is no way of really knowing how much of that is digestible and how much indigestible. Digestible fibre is used for energy in much the same way as carbohydrate. There is also no minimum length of fibre required, so if the fibre used is too short then the total fibre quoted can again be misleading.
One mistake often made when feeding rabbits is to assume that fibre which is indigestible for humans is also indigestible for rabbits. Bran may provide roughage for people, but for rabbits it is a source of energy. Bran mash was a common feed given to rabbits in the war years.
Selective eating can lead to health issues
Rabbits are selective feeders and may refuse to eat certain ingredients in a mix leading to dietary imbalance and health problems. The coloured biscuits, grains and pulses in rabbit mixes would not normally form a part of the natural rabbit diet and manufacturers compensate for this by adding extra calcium and fibre to the pellets in the mix to balance the excess phosphorous in the grains and the lack of fibre in those other ingredients.
A rabbit which eats only the biscuits and flakes from a mix runs the risk of calcium deficiency and slow transit time through the gut (leading to dysbiosis). A rabbit eating only the balancer pellets from a mix would be consuming excess calcium which might cause problems if not excreted. Fortunately rabbits have the ability to excrete excess calcium in their urine, leaving a white ‘tide mark’. If the levels are too high then the rabbit may develop gravel in the urine or calculi (stones)