Dental care in rabbits
Rabbits are herbivores and have very different teeth to dogs and cats. Their teeth grow continually throughout the rabbit's life and are constantly worn down by chewing harsh grass and hay. The commonest problem in rabbit's teeth is overgrowth as a consequence of the teeth not aligning correctly and therefore not being worn down. This can occur in just the incisors (front teeth) or can involve the molars (back teeth) too. The incisors can be burred back into shape conscious, but to correct the molars a general anaesthetic is required (which the rabbit to the right is being prepared for).
In some cases, the overgrowth is simply a consequence of misalignment, but in most cases the cause is poor tooth growth and diseased tooth roots as a consequence of dietary deficiencies, particularly of minerals.
The main staple of a rabbit's diet should be grass or hay, which should be available at all times. This gives the a good source of fibre to maintain gut health and contains a fair amount of the minerals required for healthy teeth. It also gives their teeth something to work on to grind down the continual growth.
Rabbit mixes are also usually fed to provide greater amounts of energy, protein and mineral than is available from just grass. The problem arises when these mixes are available ad lib (i.e. all the time and never runs out). Some rabbits will selectively eat their favourite bits, filling themselves with these. They usually leave out the hard pellets containing the minerals, and also don't eat as much grass or hay. The consequence is a fat, mineral deficient rabbit with poor gut health, leading to overgrown teeth, tooth root abscesses and often a mucky backside. Only as much mix as will be finished in half an hour should be fed once or twice daily.
Another way to avoid selective feeding is to buy a pelleted feed rather than a mix, but this is still no substitute for grass or hay.